{"dataset":"anvilfield-calculators","description":"Free field-calculator metadata by trade.","source":"https://anvilfield.com/","license":"CC BY 4.0","attribution":"Anvilfield (anvilfield.com)","count":71,"records":[{"slug":"aggregate-base-tonnage-calculator","trade":"paving","url":"https://anvilfield.com/calculators/aggregate-base-tonnage-calculator/","title":"Aggregate base tonnage calculator (crushed stone)","short_title":"Aggregate base calculator","dek":"Find the tons of crushed aggregate base for a given area and compacted depth.","intro":"Crushed aggregate base is the compacted stone layer under a pavement, slab, or unpaved road, and it is sold by the ton, so estimating it means converting an area and a depth into tonnage. The tonnage is the area times the compacted depth times the material density, divided by 2000. Enter the area in square feet, the compacted depth in inches, and the compacted density in pounds per cubic foot. Crushed aggregate base typically runs about 135 to 150 pcf compacted depending on the gradation and the stone, so 140 is a reasonable default to start from. The tool returns the in-place compacted tonnage and the equivalent cubic yards. Two cautions keep the order honest. This is the compacted in-place quantity, so the loose material delivered is more because it compacts down under rolling, and you should add for waste and over-excavation, commonly 10 to 20 percent. Confirm the design depth, the material specification, and the compacted density with the geotechnical engineer and the project specification, since the base thickness is set by the subgrade and the traffic, not a rule of thumb."},{"slug":"air-changes-per-hour-cfm-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/air-changes-per-hour-cfm-calculator/","title":"Air changes per hour calculator (ACH to CFM)","short_title":"ACH to CFM calculator","dek":"Find the airflow for a target air change rate: CFM = room volume x ACH / 60, from floor area and ceiling height.","intro":"Air changes per hour is a quick way to size ventilation or exhaust for a space, and it converts straight to airflow. The CFM needed equals the room volume times the target ACH divided by 60, and the volume is the floor area times the ceiling height. Enter the area, the height, and the target air change rate. One air change is a full replacement of the room's air, so spaces that are specified in ACH (restrooms, commercial kitchens, mechanical and battery rooms, labs, parking garages) translate directly into a fan or supply CFM with this formula. To run it backward and check an existing system, ACH equals CFM times 60 divided by the volume. Treat ACH as a rule-of-thumb target rather than a design in itself: a real ventilation design uses a load calculation or a ventilation-rate method such as ASHRAE 62.1, which sets outdoor air by the number of people and the floor area, so confirm the required rate against the code and the application before sizing equipment."},{"slug":"ashrae-ventilation-rate-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/ashrae-ventilation-rate-calculator/","title":"ASHRAE 62.1 ventilation rate calculator","short_title":"Ventilation rate calculator","dek":"Find the breathing-zone outdoor air a space needs: Vbz = Rp x Pz + Ra x Az.","intro":"Outdoor air for ventilation is sized two ways at once: enough for the people and enough for the space itself, and ASHRAE 62.1 adds them. The breathing-zone outdoor airflow Vbz equals the per-person rate Rp times the number of people Pz, plus the per-area rate Ra times the zone area Az. Enter the four values. Typical office numbers are about 5 cfm per person and 0.06 cfm per square foot, but the correct rates come from the occupancy-category table in the standard, which varies a lot by space type (classrooms, gyms, labs, and patient rooms are all different). The result is the breathing-zone requirement. To get the zone outdoor airflow you divide by the zone air distribution effectiveness Ez, which is around 0.8 when warm air is supplied from the ceiling and up to 1.0 with good mixing, so poor distribution means more outdoor air. At an air handler serving several zones, the multiple-spaces equation and the system ventilation efficiency adjust the total again, usually downward but never below any single zone's need. Use the rates, effectiveness values, and full procedure from the adopted edition of ASHRAE 62.1, and confirm the design with the mechanical engineer."},{"slug":"asphalt-in-place-density-gmm-calculator","trade":"paving","url":"https://anvilfield.com/calculators/asphalt-in-place-density-gmm-calculator/","title":"Asphalt in-place density (% Gmm and air voids) calculator","short_title":"Asphalt density calculator","dek":"Turn a mat density reading and the Gmm into % Gmm and air voids, and check it against the acceptance target before the lot cools.","intro":"In-place density is the headline acceptance number on an asphalt mat, and it is reported as a percent of Gmm, the maximum theoretical specific gravity (the Rice value). This calculator converts a mat density reading in pounds per cubic foot to % Gmm and air voids: % Gmm = density / (Gmm x 62.4), and air voids = 100 minus % Gmm. Enter the in-place density from the gauge or a core, the Gmm from the lab (AASHTO T209 / ASTM D2041), and the acceptance target. The common dense-graded field target is about 92 to 93 percent of Gmm, the same as 7 to 8 percent air voids, and the longitudinal joint is usually held a point or two lower because that seam is where density and pavement life go to die. The catch is timing: this is the number you either hit or miss while the mat is above its cessation temperature (commonly near 175 to 185 F), because once the binder sets you cannot roll density back in. Put a clock on the mat with the compaction-window tool before you pave, and confirm the acceptance target, the gauge correlation, and the Rice method with the agency specification."},{"slug":"asphalt-tonnage-calculator","trade":"paving","url":"https://anvilfield.com/calculators/asphalt-tonnage-calculator/","title":"Asphalt tonnage calculator","short_title":"Asphalt tonnage calculator","dek":"Estimate the tons of hot-mix asphalt for a job from length, width, compacted thickness, and the mix unit weight, with a waste allowance.","intro":"Enter the length and width in feet, the compacted thickness in inches, and the mix unit weight (compacted hot-mix asphalt runs about 145 to 150 lb per cubic foot, so 145 is the default). The calculator returns the tons to order and a 10 percent allowance for waste, joints, and yield. Confirm the unit weight and the final order with the asphalt plant."},{"slug":"battery-ups-runtime-calculator","trade":"datacenter","url":"https://anvilfield.com/calculators/battery-ups-runtime-calculator/","title":"Battery and UPS runtime calculator","short_title":"UPS runtime calculator","dek":"Estimate how long a battery or UPS holds a load: runtime = usable kWh x efficiency / load kW.","intro":"When utility power drops, the only thing between the load and a hard outage is the battery, and the first question is always how long it lasts. The runtime in minutes is roughly the usable battery energy times the inverter efficiency, divided by the load, times sixty. Enter the usable battery capacity in kilowatt-hours, the critical load in kilowatts, and the inverter or UPS efficiency as a percent. The result is a planning estimate, and real runtime is almost always shorter for several reasons worth understanding. Battery capacity falls as the discharge rate rises, an effect called Peukert's law that hits VRLA lead-acid hardest, so a battery drained fast delivers less than its slow-rate rating. Usable capacity is also less than the nameplate amp-hours, and capacity fades with age and temperature, which is why designers size around end-of-life numbers rather than a fresh battery. To convert amp-hours to kilowatt-hours, multiply amp-hours by the battery voltage and divide by one thousand. Use this to sanity-check the autonomy and the window to start a generator or transfer power, and confirm the real sizing with the UPS and battery manufacturer."},{"slug":"bolt-torque-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/bolt-torque-calculator/","title":"Bolt torque calculator (T = K x D x F)","short_title":"Bolt torque calculator","dek":"Estimate bolt torque from the target preload: T = K x D x F, where K is the nut factor.","intro":"Torque is the practical stand-in for the clamp force a bolt actually delivers, and the short-form equation links them: torque equals the nut factor K times the bolt nominal diameter D times the target preload F. Enter the diameter in inches, the preload in pounds, and a K value to get the torque in inch-pounds and foot-pounds. The whole calculation lives and dies on K, the nut factor, which rolls the thread friction and the friction under the nut or bolt head into one number. K runs around 0.2 for plain dry steel, drops when the threads are lubricated, and climbs when they are rusty or galvanized, and because torque scales directly with it, the same preload can need very different torque depending on the condition of the fastener. Treat this as an estimate for when you genuinely know the preload and a defensible K. For any real joint, electrical lug, or structural connection, use the published torque value from the equipment manufacturer, the engineer, or the governing standard (such as RCSC for high-strength structural bolts), along with the specified tightening method like turn-of-nut, direct-tension indicators, or a calibrated wrench."},{"slug":"bulk-material-volume-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/bulk-material-volume-calculator/","title":"Mulch, gravel, and soil volume calculator","short_title":"Bulk material calculator","dek":"Estimate the cubic yards, cubic feet, bags, and tons of mulch, gravel, topsoil, or sand for a bed or area from length, width, and depth.","intro":"Enter the bed or area length and width in feet and the depth in inches. The calculator returns the volume in cubic yards and cubic feet, the number of 2-cubic-foot bags, and (if you add a unit weight) a tonnage estimate. Mulch is light, while screened topsoil, sand, and gravel are heavy, so confirm the unit weight and the final order with the supplier and add a little extra for settling."},{"slug":"cmu-block-mortar-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/cmu-block-mortar-calculator/","title":"CMU block calculator (blocks and mortar)","short_title":"CMU block calculator","dek":"Find blocks and mortar for a wall: about 1.125 standard 8x8x16 blocks per square foot, plus a bag of mortar per 28 to 32 blocks.","intro":"Ordering for a block wall comes down to the wall area and the size of the unit. A standard 8 by 8 by 16 inch concrete masonry unit has a nominal 8 by 16 inch face once the mortar joint is included, which covers about 0.89 square feet, so a wall needs roughly 1.125 blocks per square foot. Enter the wall area, with door and window openings deducted, and a waste percentage for cuts and breakage. Mortar runs about one 80 pound bag for every 28 to 32 blocks, often stated as roughly three bags per hundred block. This calculator counts the blocks and the mortar; order grout, rebar, and horizontal joint reinforcement separately based on the reinforcement schedule, since grouted and reinforced walls need fill and steel the block count does not capture. Yields shift with the block size, the joint thickness, and the mortar type, so confirm the unit dimensions and the bag yield with your supplier before the order."},{"slug":"concrete-bags-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/concrete-bags-calculator/","title":"Concrete bags calculator (bags from volume)","short_title":"Concrete bags calculator","dek":"Find how many bags of concrete a job needs: bags = volume (cubic feet) divided by the yield per bag, plus waste.","intro":"For a small pour, the question is how many bags to buy, and the answer is the volume divided by what one bag yields. Bags needed equals the concrete volume in cubic feet divided by the yield per bag, plus a little waste for spillage and overpack. Enter the volume, the bag yield (the cubic feet of mixed concrete one bag makes), and a waste percentage. Typical yields are about 0.60 cubic feet for an 80 pound bag, 0.45 for a 60 pound bag, and 0.375 for a 50 pound bag, but the figure is printed on the bag and varies by mix, so use the real number. To get the volume, multiply length by width by thickness in feet, remembering a 4 inch slab is 0.333 feet thick and a 6 inch slab is 0.5 feet. Bagged mix is the right call for posts, equipment pads, footings, and repairs; once the job passes roughly one cubic yard (27 cubic feet) ready-mix delivery is usually cheaper and far less labor."},{"slug":"concrete-formwork-pressure-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/concrete-formwork-pressure-calculator/","title":"Concrete formwork pressure calculator (ACI 347)","short_title":"Formwork pressure calculator","dek":"Estimate the lateral pressure of fresh concrete on column forms: P = Cw x Cc x (150 + 9000R/T).","intro":"Fresh concrete behaves like a heavy fluid as it is placed, pushing outward on the forms, and that lateral pressure is what the ties, sheathing, walers, and shores have to resist. The ACI 347 formula for columns is P equals Cw times Cc times the quantity 150 plus 9000 times R divided by T, where R is the rate of placement in feet per hour and T is the concrete temperature in degrees Fahrenheit. This calculator takes the unit-weight coefficient Cw and the chemistry coefficient Cc as 1.0, which fits normal-weight concrete with no set retarders or special admixtures; for lightweight mixes, retarded concrete, or blended cements those coefficients change, so adjust them per ACI 347. The design pressure is bounded by a minimum of 600 psf and a maximum of 3000 psf, or the full hydrostatic head of the concrete, whichever is less. The takeaway for the field is that a fast pour in cold concrete builds the highest pressure, which is exactly when forms blow out, so the pour rate is a safety control, not just a schedule choice. Walls use a different formula and rate ranges. Treat this as a planning figure and confirm the design pressure and the formwork design with ACI 347 and the engineer."},{"slug":"concrete-yardage-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/concrete-yardage-calculator/","title":"Concrete yardage calculator","short_title":"Concrete yardage calculator","dek":"Figure the cubic yards for a slab or footing from length, width, and thickness, with a waste allowance so you do not come up short.","intro":"Enter the length, width, and thickness of the pour and a waste allowance, and the calculator returns the cubic yards to order. Running short mid-pour means a cold joint, so most crews add 5 to 10 percent. Confirm the final number and the mix with the ready-mix supplier."},{"slug":"cooling-tons-btu-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/cooling-tons-btu-calculator/","title":"Cooling tons calculator (BTU to tons)","short_title":"Tons to BTU calculator","dek":"Convert a cooling load to tons of refrigeration: tons = BTU per hour divided by 12,000.","intro":"Cooling equipment is rated in tons, and converting a load between BTU per hour and tons is one of the most common quick checks in the field. The conversion is tons = BTU per hour divided by 12,000, because one ton of refrigeration equals 12,000 BTU per hour, the rate of heat removal to melt one ton of ice over a day. Enter the cooling load in BTU per hour to get the tonnage and the equivalent thermal kilowatts; to go the other way, multiply tons by 12,000 to get BTU per hour. One thing to keep straight: this is a unit conversion of a load you already know, not a load calculation, so the BTU per hour figure should come from a proper Manual J or block load study rather than a rough rule of thumb per square foot, which oversizes equipment and hurts comfort and humidity control. Keep the thermal tonnage separate from the electrical kilowatts the compressor and fans actually draw, which depend on the equipment efficiency, and select and size the equipment with the manufacturer performance data and the engineer."},{"slug":"crane-sling-leg-load-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/crane-sling-leg-load-calculator/","title":"Crane sling load calculator (leg tension by angle)","short_title":"Sling load calculator","dek":"Find the tension in each sling leg: (load weight / legs) divided by the sine of the sling angle from horizontal.","intro":"The danger in rigging is that a sling at an angle carries far more than the load it lifts. Each leg's tension equals the load weight divided by the number of legs, divided by the sine of the sling angle measured from horizontal. Enter the load, the leg count, and the angle to get the tension per leg and the load factor. The angle drives everything: at 90 degrees (a straight vertical pull) each leg carries only its share, but as the legs spread and the angle drops, the tension multiplies. The load factor is 1.41 at 60 degrees, 2.0 at 30 degrees, and it climbs toward infinity as the angle approaches horizontal, which is why slings are rated down to a minimum angle and most riggers refuse to work below 30 degrees. Two more cautions: a four-leg bridle on a rigid load often rides on just two legs, so do not assume even sharing, and the choke or basket hitch changes the capacity. Treat this as a planning number, rig to the sling and hardware rated capacity for the actual angle, and use a qualified rigger."},{"slug":"debris-dumpster-volume-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/debris-dumpster-volume-calculator/","title":"Debris dumpster calculator (container count)","short_title":"Dumpster calculator","dek":"Find how many roll-off containers a job needs: loose debris volume divided by the container size, in cubic yards.","intro":"Ordering containers for a demolition or cleanup job comes down to how much debris you will make and how big the box is. The number of containers is the loose debris volume divided by the container size, both in cubic yards. Enter the volume and the box size; common roll-offs run 10, 20, 30, and 40 cubic yards. Estimate the volume as length times width times the pile height in feet, divided by 27. Two cautions keep the estimate honest. Demolished material bulks up as it is torn out, so the loose volume you haul is larger than the neat in-place volume. And weight, not volume, is often the real limit: heavy debris like concrete, masonry, dirt, asphalt, and shingles hits the container weight cap long before the box looks full, which is why haulers put those in smaller dedicated boxes. Confirm the size mix and the weight limits with your hauler."},{"slug":"deck-board-count-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/deck-board-count-calculator/","title":"Deck board count calculator","short_title":"Deck board calculator","dek":"Find the deck boards for a deck: boards = deck area divided by the coverage of one board, plus waste.","intro":"Estimating decking comes down to the area divided by what one board covers, plus waste. Enter the deck area in square feet, the board width in inches (5.5 for a standard 5/4 by 6 deck board), the board length in feet, and a waste allowance, and the tool returns the number of boards and the total linear feet. Two things push the waste up and catch estimators short: the gap between boards, about an eighth to three-sixteenths of an inch, slightly reduces the real coverage per board, and a picture-frame border, a diagonal or herringbone pattern, or a run of stair treads all generate cut-offs, so a 10 to 15 percent allowance is typical and a cut-up or angled deck needs more. This counts the decking boards only, so order the joists, beams, ledger, footings, fasteners or hidden clips, and the railing separately. One more thing to confirm before you buy: composite and PVC decking often require tighter joist spacing than wood and have their own fastening systems, so check the decking manufacturer's installation requirements."},{"slug":"dehumidifier-sizing-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/dehumidifier-sizing-calculator/","title":"Dehumidifier sizing calculator (water restoration)","short_title":"Dehumidifier sizing","dek":"Size dehumidification for a water loss: AHAM pints per day = affected volume divided by the class factor.","intro":"Sizing the dehumidification for a water loss is what keeps the structure drying fast enough to beat mold, and the conventional IICRC S500 method is simple: divide the affected volume in cubic feet by a class factor to get the AHAM pints per day of dehumidification needed. Enter the room length, width, and ceiling height, and the class factor. The factor gets smaller as the water class gets wetter, so a wetter room calls for more dehumidification: for a low-grain-refrigerant (LGR) dehumidifier the factors run roughly 100 for class 1, 50 for class 2, 40 for class 3, and about 45 for class 4, but the exact factor depends on the dehumidifier type, standard refrigerant versus LGR versus desiccant, and the version of the method you follow. Take the pints-per-day result and divide it by the AHAM rating of the dehumidifier you are placing to get the number of units, then pair them with enough air movers to keep evaporation feeding the dehumidifiers. Treat this as a starting estimate, confirm the class and the factor against the IICRC S500 and the manufacturer data, and monitor the drying daily to a documented dry standard rather than to the equipment count."},{"slug":"dew-point-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/dew-point-calculator/","title":"Dew point calculator (temperature and humidity)","short_title":"Dew point calculator","dek":"Find the dew point from air temperature and relative humidity, and the surface temperature condensation forms at.","intro":"The dew point is the temperature at which air becomes saturated and water condenses out, and it decides a surprising number of field problems. Enter the air temperature in degrees Fahrenheit and the relative humidity as a percent, and the tool returns the dew point using the Magnus approximation. Any surface at or below the dew point will grow condensation, which is the root of several jobsite headaches: painters and coatings crews keep steel at least 5 degrees Fahrenheit above the dew point before they coat, because moisture under a coating makes it fail; cold water pipe and chilled-water duct sweat and need insulation and a vapor barrier; and a freezer or cold-storage box drives a relentless inward vapor problem for the same reason. Higher humidity and higher air temperature both push the dew point up. Treat the result as a field estimate, and confirm critical coating or condensation decisions with a calibrated psychrometer or sling hygrometer and the coating manufacturer's surface-temperature rule."},{"slug":"drip-irrigation-runtime-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/drip-irrigation-runtime-calculator/","title":"Drip irrigation run time calculator","short_title":"Drip run time calculator","dek":"Find a drip zone's precipitation rate and run time: rate = GPH x 1.604 / area, and run time = target depth divided by the rate.","intro":"Setting a drip zone by guesswork either drowns the plants or starves them. This calculator turns the zone's flow and area into a precipitation rate, then gives the run time to apply a target depth of water. The rate in inches per hour equals the zone flow in gallons per hour times 1.604, divided by the irrigated area in square feet, since one inch of water over one square foot is 0.623 gallons. The run time for a target depth is that depth divided by the rate. Enter the zone flow in GPH, the irrigated area in square feet, and the target depth in inches. Drip applies water slowly and efficiently and goes straight to the root zone, but a long single run on slow-draining soil or a slope can still run off, so split it into shorter cycles with soak time between. Tune the schedule to the plant water need, the soil intake rate, and the weather or evapotranspiration rather than a fixed clock, and confirm against the manufacturer emitter data."},{"slug":"drywall-sheet-count-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/drywall-sheet-count-calculator/","title":"Drywall sheet calculator (board count)","short_title":"Drywall sheet calculator","dek":"Find how many drywall sheets a job needs: area to cover divided by the sheet size, plus waste.","intro":"Estimating drywall is the area to cover divided by the size of a sheet, plus a little waste. Enter the total area of walls plus ceilings and the sheet size in square feet. A 4 by 8 sheet is 32 square feet, a 4 by 10 is 40, and a 4 by 12 is 48. Larger sheets leave fewer joints to tape and finish, which is faster and looks better, but they are heavier and harder to maneuver, so crews use the long sheets on open walls and ceilings and the 4 by 8 in tight rooms and stairwells. A 10 percent waste allowance is typical; bump it up on a cut-up job with lots of windows, doors, and short walls where the offcuts pile up. This counts the board only, so order the joint compound, tape, corner bead, and screws separately, and confirm the board type and thickness needed for the fire rating and the location (moisture-resistant in wet areas, Type X where the assembly is rated)."},{"slug":"duct-equivalent-diameter-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/duct-equivalent-diameter-calculator/","title":"Equivalent round duct diameter calculator","short_title":"Duct equivalent diameter","dek":"Convert a rectangular duct to its equal-friction round diameter: De = 1.30 x (a x b)^0.625 / (a + b)^0.250.","intro":"Duct is sized from a friction rate in round dimensions, then converted to a rectangular duct that fits the available space, and the link between the two is the equivalent round diameter. The formula is De = 1.30 times (a times b) to the 0.625 power, divided by (a plus b) to the 0.250 power, with the rectangular sides a and b in inches. Enter the two sides to get the round duct that carries the same airflow at the same friction loss. The point that trips people up is that the equivalent is matched on friction, not on cross-sectional area, so a rectangular duct sized this way actually has a larger area than the round it replaces. The calculator also reports the aspect ratio, the long side divided by the short side. Keep that under about 4 to 1, because a flat, high-aspect duct burns more sheet metal, adds friction and noise, and costs more to fabricate and hang. Size the system from the design friction rate and confirm the final layout with the mechanical engineer."},{"slug":"energy-cost-kwh-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/energy-cost-kwh-calculator/","title":"Energy cost calculator (kWh and dollars)","short_title":"Energy cost calculator","dek":"Find what a load costs to run: kWh = kW x hours, times the rate per kWh, per day and per year.","intro":"Putting a dollar figure on a running load is the starting point for any efficiency, retrofit, or operating-cost decision. The energy used per day equals the load in kilowatts times the hours it runs, and the cost equals those kilowatt-hours times the rate in dollars per kWh, multiplied by 365 for the year. Enter the load, the run hours, and your rate. To get the kW from a nameplate in watts, divide by 1000, and for a motor or variable load use the real running draw rather than the nameplate maximum. This calculator covers the energy (consumption) charge, which is exactly what an LED lighting retrofit, a high-efficiency motor or VFD, or a scheduling change reduces, so it is handy for sizing the payback on an upgrade. Remember a commercial bill also carries demand charges billed on the monthly peak demand in kW, plus fixed customer fees and taxes, so for a real number use the utility's actual rate schedule and tariff, not just the energy rate."},{"slug":"excavation-truck-load-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/excavation-truck-load-calculator/","title":"Excavation truck load calculator (haul-off)","short_title":"Truck load calculator","dek":"Find how many truck loads to haul off an excavation: loose volume = bank volume x (1 + swell), divided by truck capacity.","intro":"Hauling off an excavation costs by the truck load, and the number of loads is not just the size of the hole, because soil expands when you dig it. The loose volume you actually haul is the in-place (bank) volume times one plus the swell factor, divided by the truck capacity. Enter the bank cubic yards (the volume of the cut or hole measured in place), the swell or bulking percentage, and the truck box capacity. The swell depends on the soil: sand and gravel expand roughly 10 to 15 percent, common earth around 25 percent, clay 30 to 40 percent, and blasted rock much more, so the loose volume hauled is always larger than the neat excavation. Two cautions keep the estimate honest. Dump trucks are often limited by legal weight rather than box volume on heavy, wet, or rocky material, so the real load can be smaller than the box suggests. And the reverse happens at a fill, where the soil compacts down by a shrink factor. Confirm the swell with the geotechnical report and the legal haul weight with the trucking company."},{"slug":"fall-clearance-calculator","trade":"roofing","url":"https://anvilfield.com/calculators/fall-clearance-calculator/","title":"Fall clearance calculator (fall arrest)","short_title":"Fall clearance calculator","dek":"Find the clearance a personal fall arrest system needs below the anchor: free fall + deceleration + worker height + a safety margin.","intro":"A personal fall arrest system only protects the worker if there is enough open distance below them to stop the fall before they hit the lower level. This calculator adds the four parts of required fall clearance: the free fall distance before the system starts to slow the worker, the deceleration distance as a shock-absorbing lanyard or self-retracting lifeline pays out and stops the fall, the worker height from the dorsal D-ring down to the feet, and a safety margin. Enter each in feet. A common 6-foot shock-absorbing lanyard tied off at foot level can need roughly 18.5 feet of clearance below the anchor, which is why short falls into a floor below are a real hazard and why a self-retracting lifeline or a higher anchor is often the answer. Treat the result as a planning number, confirm it against the specific equipment manufacturer instructions and OSHA and ANSI Z359, and account for the anchor height and any swing-fall, which change the real clearance needed."},{"slug":"fan-pump-affinity-laws-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/fan-pump-affinity-laws-calculator/","title":"Fan and pump affinity laws calculator","short_title":"Affinity laws calculator","dek":"Scale fan or pump flow, pressure, and power for a speed change using the affinity laws: flow with speed, pressure with the square, power with the cube.","intro":"The affinity laws describe how a fan or pump responds when you change its speed with the impeller diameter fixed. Flow varies directly with speed, pressure or head varies with the square of the speed, and power varies with the cube. Enter the old and new speed (RPM or percent speed) and any value you know now, the flow in CFM or GPM, the pressure or head, or the brake power in horsepower, and the calculator scales each one to the new speed. The cube law on power is the reason a variable frequency drive saves so much energy: slowing a fan to 80 percent speed drops the power draw to roughly half. Treat these as ideal relationships and confirm the operating point against the actual fan or pump curve and the system curve, since the system curve and static head shift the real result."},{"slug":"fence-post-material-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/fence-post-material-calculator/","title":"Fence post and section calculator","short_title":"Fence post calculator","dek":"Find the posts, sections, and rails for a fence run: sections = length divided by post spacing.","intro":"Estimating a fence starts with the sections and posts: the run length divided by the post spacing gives the sections, the line posts are the sections plus one, and the rails are the sections times the rails per section. Enter the fence length in feet, the post spacing in feet (6 and 8 are common), and the rails per section. The result covers one straight run, and the most common estimating miss is the extras: every corner, every end, and every gate gets its own post, and gate and corner posts are heavier and set deeper because they take the swing of the gate and the pull of the fence on both sides. Setting depth matters as much as count: line posts go roughly one-third of their length into the ground and below the local frost line, set in concrete for most fence types. And watch the wind, because a solid privacy fence acts like a sail and needs deeper, stronger posts and footings than an open picket or chain-link run of the same height. Use this to size the material order, then confirm the post depth, the spacing, the footing size, and any wind-load requirements with the manufacturer and the local code and AHJ."},{"slug":"footcandle-lighting-fixture-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/footcandle-lighting-fixture-calculator/","title":"Footcandle lighting calculator (fixture count)","short_title":"Footcandle calculator","dek":"Estimate fixtures for a target light level: target lumens = area x footcandles, divided by the lumens each fixture delivers.","intro":"This calculator gives a fast, average-level estimate of how many fixtures a space needs to hit a target light level, using the lumen method. A footcandle is one lumen per square foot, so the target lumens equal the area times the target footcandles, and the fixture count is that total divided by the lumens each fixture actually delivers after losses. Enter the area in square feet, the target footcandles for the task (the IES recommends levels by space and activity), the rated lumens per fixture, and a combined factor that rolls light-loss and room utilization into one number, often around 0.7 and lower in tall or dark-finished rooms. The result is a planning ballpark for fixture quantity and budget. A real lighting design uses the fixture coefficient of utilization, room cavity ratios, spacing criteria, and a point-by-point photometric layout to check uniformity and glare, so confirm the final design with a photometric study against the IES target."},{"slug":"footing-bearing-pressure-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/footing-bearing-pressure-calculator/","title":"Footing bearing pressure calculator (soil)","short_title":"Bearing pressure calculator","dek":"Check soil bearing pressure under a footing: pressure = load divided by footing area.","intro":"A spread footing works by spreading a concentrated column or wall load over enough soil that the ground can carry it without overloading or settling, and the quick check is the bearing pressure: the load divided by the footing area. Enter the service load in pounds and the footing length and width in feet, and optionally the allowable soil bearing pressure to check against. The tool returns the pressure the footing puts on the soil and, if you enter an allowable value, whether the footing is within it. When the pressure exceeds the allowable, the footing has to be made larger or the load reduced. Two cautions keep this honest. This is a fast service-load check, not a footing design, and the allowable bearing capacity is not a number to guess: it comes from the geotechnical report for that site and soil. And the real footing design, the reinforcement, the punching-shear and one-way shear checks, the settlement analysis, and the governing load combinations, is the structural engineer's work. Use this to size or sanity-check a footing, then confirm the bearing value with the geotechnical engineer and the design with the structural engineer of record."},{"slug":"generator-runtime-fuel-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/generator-runtime-fuel-calculator/","title":"Generator runtime calculator (fuel hours)","short_title":"Generator runtime calculator","dek":"Find how long a generator runs: usable fuel in gallons divided by the consumption in gallons per hour.","intro":"Planning a generator for an outage or a standby duty starts with how long it will run on the fuel you have. The runtime in hours equals the usable fuel in gallons divided by the fuel consumption in gallons per hour. Enter the tank capacity, the burn rate, and a reserve percentage to hold back so you are not running the tank dry. The number that moves the most is the burn rate, because fuel consumption tracks the electrical load: a diesel generator burns roughly 0.05 to 0.08 gallons per hour per kW near full load and proportionally less when lightly loaded, so use the consumption at your actual load from the manufacturer's data rather than a single fixed figure. For an extended outage, plan a fuel reserve, a refueling contract, and fuel maintenance, since stored diesel degrades over time and water and microbial growth foul it, which is also why standby tanks get periodic polishing. Confirm the runtime against the manufacturer's load-versus-consumption curve."},{"slug":"generator-sizing-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/generator-sizing-calculator/","title":"Generator sizing calculator (running + surge)","short_title":"Generator sizing calculator","dek":"Size a generator from the running load plus the largest motor's starting surge, with headroom: peak = running + surge.","intro":"A generator is undersized if it cannot carry everything running at once plus the jolt when the biggest motor starts. This calculator adds the total running watts of the loads that will be on together to the momentary starting surge of the largest motor, then applies a headroom percentage to land on a recommended size. Motors are the catch: an air conditioner, well pump, or compressor can pull several times its running watts for a moment on start, and that inrush sets the peak the generator must swallow without stalling or sagging the voltage. Enter the total running load in watts, the extra starting surge of the largest motor, and a headroom percentage. Build the running total from actual nameplate watts, use the locked-rotor or starting figures for the surge, and confirm the size, fuel type, and power factor against the equipment and the generator manufacturer, along with NEC sizing for the conductors, overcurrent, and transfer equipment."},{"slug":"hvac-duct-airflow-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/hvac-duct-airflow-calculator/","title":"Duct airflow (CFM and velocity) calculator","short_title":"Duct airflow calculator","dek":"Solve duct airflow and velocity from the duct size using continuity (Q = V x A): enter a round or rectangular duct and either the CFM or the velocity, and get the other.","intro":"Pick the duct shape and enter the size: a round diameter, or a rectangular width and height in inches. Then enter either the airflow in CFM or the velocity in feet per minute, and leave the other blank to solve it. The calculator works the continuity relationship Q = V x A, where Q is CFM, V is the velocity, and A is the duct free area in square feet. Use it to size a duct for a target velocity, or to check the velocity a given duct carries at a given CFM. Comfort branch ducts commonly run around 700 to 1200 fpm and trunks higher, but confirm the airflow and the velocity and noise limits against the design and the balancing report."},{"slug":"hydronic-load-gpm-delta-t-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/hydronic-load-gpm-delta-t-calculator/","title":"Hydronic load calculator (GPM, delta-T, tons)","short_title":"Hydronic load calculator","dek":"Find the heat load of a hydronic loop from flow and temperature difference: BTU/hr = GPM x 500 x delta-T, and tons = GPM x delta-T / 24.","intro":"This calculator works the basic hydronic heat-transfer relationship for water: heat rate in BTU per hour equals the flow in gallons per minute times 500 times the temperature difference (delta-T) across the coil, chiller, or boiler. Tons of cooling is that BTU/hr divided by 12,000, which is the same as GPM times delta-T divided by 24. Enter the delta-T and either the flow or the load, and the rest is solved. Use it to check a chiller or boiler against its design flow and delta-T, to size a pump to a load, or to spot a low delta-T problem where the flow is high but the load is not there. The 500 constant is 8.33 lb per gallon times 60 minutes times the specific heat of water; a glycol mix carries less heat per gallon, so drop the constant to roughly 480 to 490 and confirm the fluid properties and the equipment data before you commit."},{"slug":"insulation-r-value-thickness-calculator","trade":"roofing","url":"https://anvilfield.com/calculators/insulation-r-value-thickness-calculator/","title":"Insulation R-value thickness calculator","short_title":"R-value thickness calculator","dek":"Find the insulation thickness for a target R-value: thickness = target R divided by the material's R per inch.","intro":"Hitting a required R-value comes down to how much R each inch of the chosen insulation delivers. The thickness needed is simply the target R-value divided by the material's R-value per inch. Enter the target R and the product R-per-inch to get the thickness. The R-per-inch varies widely by material: fiberglass and mineral wool batt sit lower, while polyiso, extruded and expanded polystyrene, and closed-cell spray foam sit higher, and polyiso de-rates in cold temperatures, so always use the specific product datasheet rather than a generic number. Remember the value this gives is for the insulation layer alone. The whole-assembly R is pulled down by framing and other thermal bridging and added to by the sheathing, air films, and other layers, so for a roof, wall, or ceiling, confirm the code-required assembly R for the climate zone against the energy code, not just the insulation R."},{"slug":"irrigation-precipitation-rate-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/irrigation-precipitation-rate-calculator/","title":"Irrigation precipitation rate calculator","short_title":"Precipitation rate calculator","dek":"Find how fast a zone applies water: PR (in/hr) = 96.25 x total gpm / zone area, and the run time to hit a target depth.","intro":"The precipitation rate is how fast an irrigation zone puts water on the ground, and it is what sets the run time and whether water soaks in or runs off. The rate in inches per hour equals 96.25 times the total flow in gallons per minute applied to the zone, divided by the zone area in square feet. Enter the combined flow of every head running on the zone and the area they cover. Once you know the rate, the run time follows: minutes equals the target depth in inches divided by the precipitation rate, times sixty. Two cautions make the number useful in the field. The application rate must not exceed the soil's intake rate, or water sheets off and is wasted and erosive, so on slopes and tight clay soils split the watering into several short cycles with soak time between them, which is called cycle and soak. And every head on a single zone should be a matched-precipitation type, so the rate is even across the area rather than flooding some spots while leaving others dry. Treat this as a scheduling estimate, verify it against a catch-can audit, and follow the local watering restrictions."},{"slug":"kva-to-amps-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/kva-to-amps-calculator/","title":"kVA to amps calculator","short_title":"kVA to amps calculator","dek":"Convert kVA to full-load amps (or amps back to kVA) for single-phase and three-phase, from the voltage.","intro":"Enter the system and the voltage, then fill in kVA or amps and leave the other blank to solve it. The result is the full-load current, which is the starting point for sizing the conductor, the overcurrent device, and the transformer; apply the code factors from there."},{"slug":"ladder-angle-setback-calculator","trade":"roofing","url":"https://anvilfield.com/calculators/ladder-angle-setback-calculator/","title":"Ladder angle and setback calculator (4 to 1 rule)","short_title":"Ladder setback calculator","dek":"Set a ladder safely with the 4 to 1 rule: base setback = height to contact divided by four.","intro":"A ladder set at the wrong angle is one of the most common causes of a fall: too steep and it tips back, too shallow and the base kicks out. The 4-to-1 rule sets a portable extension or straight ladder at the right angle, about 75.5 degrees, by placing the base one foot away from the wall for every four feet of height up to the contact point. Enter the height where the ladder rests against the wall or the upper landing, and the tool returns the base setback, the approximate ladder span to that point, and the reach you need to access a roof or landing. Two field rules go with the math. When a ladder is used to climb onto an upper level, the side rails have to extend about three feet above that landing so there is something to hold while stepping off, which is why a roof-access ladder is longer than the wall height alone. And the ladder must be secured: tied off at the top and footed or tied at the base, with three points of contact at all times and no standing on the top two rungs. Treat this as a setup guide and follow the ladder duty rating, the manufacturer instructions, OSHA, and the site fall-protection plan."},{"slug":"markup-margin-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/markup-margin-calculator/","title":"Markup vs margin calculator","short_title":"Markup & margin calculator","dek":"Convert between markup and margin and price a job right: enter your cost and a target margin, target markup, or price, and get the price, profit, markup %, and margin %.","intro":"Markup and margin are the most-confused numbers in the trades, and mixing them up is how a job that looks profitable quietly loses money. Markup is profit divided by cost; margin is profit divided by the price. Because the denominators differ, the same dollars are always a larger markup than margin: a 50% markup is only a 33% margin. Enter your job cost, then a target margin percent, a target markup percent, or a price, and this calculator solves the rest, including the profit dollars. Price to the margin you need to cover overhead and leave real profit, then check what markup that takes. Treat the result as a starting point and confirm against your own overhead recovery and job-cost numbers."},{"slug":"mixed-air-temperature-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/mixed-air-temperature-calculator/","title":"Mixed air temperature calculator (MAT)","short_title":"Mixed air temp calculator","dek":"Find the mixed air temperature from the outdoor and return temps and the outdoor-air percentage.","intro":"When an air handler blends outdoor air with return air, the result is the mixed air temperature, the air that hits the heating or cooling coil. It is a weighted average: MAT equals the outdoor-air percentage times the outdoor temperature plus the return-air percentage times the return temperature, where the return fraction is 100 minus the outdoor fraction. Enter the outdoor temperature, the return temperature, and the outdoor-air percentage. This is a core check for testing and balancing and for economizer commissioning, because the measured mixed air should match what the damper position implies. Two cautions matter in the field. In cold weather a high outdoor-air fraction can pull the mixed air below freezing, tripping the freeze-stat or bursting a coil, so the low-limit control and the minimum outdoor-air setting matter. And real mixing boxes stratify, with cold and warm layers that do not fully blend, so a single sensor can read wrong; traverse across the duct. Confirm the design outdoor-air fraction and the readings against the balancing report and the engineer."},{"slug":"npsh-available-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/npsh-available-calculator/","title":"NPSH available calculator (pump cavitation)","short_title":"NPSH available calculator","dek":"Find the net positive suction head available to a pump: NPSHa = atmospheric + static - vapor pressure - friction head.","intro":"A pump cavitates when the suction pressure drops to the liquid's vapor pressure, flashing it to vapor that collapses on the impeller, eroding metal and killing flow. The way to prevent it is to confirm the net positive suction head available (NPSHa) beats what the pump requires. NPSHa equals atmospheric pressure head plus static suction head minus vapor pressure head minus suction friction loss, all in feet of the liquid. Enter the four heads. Atmospheric head is about 33.9 feet for water at sea level and drops with altitude and temperature. Static suction head is positive when the liquid level sits above the pump (a flooded suction) and negative when the pump has to lift liquid from below. Vapor pressure head is small for cool water, roughly 0.6 feet at 60 degrees, and climbs steeply as the liquid gets hotter, which is why hot-water and condensate pumps cavitate so easily. Friction loss is the loss through the suction pipe, fittings, and any strainer at the operating flow. The available NPSH must exceed the pump's required NPSH from the manufacturer curve with a safety margin, commonly 2 to 5 feet or more. Confirm the required NPSH and the margin with the pump manufacturer and the engineer."},{"slug":"ohms-law-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/ohms-law-calculator/","title":"Ohm's law calculator","short_title":"Ohm's law calculator","dek":"Enter any two of voltage, current, resistance, and power, and the calculator solves the rest with Ohm's law.","intro":"Enter any two of voltage, current, resistance, and power and leave the rest blank. The calculator solves the others with Ohm's law (V = I times R) and the power relationships (P = V times I). It is for a DC or resistive single-phase circuit; for AC motor and reactive loads, power factor and phase apply."},{"slug":"paint-coating-coverage-calculator","trade":"roofing","url":"https://anvilfield.com/calculators/paint-coating-coverage-calculator/","title":"Paint and coating coverage calculator (gallons)","short_title":"Coating coverage calculator","dek":"Find the paint or coating needed: gallons = area x coats / the coverage rate, plus waste.","intro":"Ordering paint or a protective coating comes down to the area, the number of coats, and how much area a gallon actually covers. The gallons needed equal the area times the number of coats divided by the coverage rate in square feet per gallon, plus a waste allowance. Enter the area, the coverage rate, the coats, and a waste percentage. The coverage rate is where estimates miss: the rate a manufacturer prints for a smooth surface drops sharply on rough, porous, textured, or profiled substrates, and a porous first coat soaks in far more than the coats over it, so a coating applied to a required film thickness covers less area than the ideal figure suggests. For roof and floor coatings the spec is usually a wet or dry mil thickness, which fixes the real coverage per gallon, so use the product datasheet rate for the actual surface and thickness rather than a generic number, and add waste for cutting in, touch-up, overspray, and the texture of the surface."},{"slug":"paver-brick-count-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/paver-brick-count-calculator/","title":"Paver and brick count calculator (by area)","short_title":"Paver count calculator","dek":"Find how many pavers or bricks an area needs: area divided by the coverage of one unit, plus a waste allowance for cuts and breakage.","intro":"Ordering pavers or brick comes down to how much area one unit covers and how much you lose to cuts. This calculator takes the area to be paved, the length and width of a single paver, and a waste percentage, then returns the count to order. Each unit covers its length times width, converted from square inches to square feet at 144 per square foot, and the count is the area divided by that coverage with the waste added on top. Enter the area in square feet, the paver dimensions in inches, and a waste percentage. A straight running bond wastes the least; herringbone, basket weave, and other patterns with many diagonal edge cuts need more. Order full bundles, keep attic stock for future repairs, and match the dye lot so a patch years later does not stand out against the field."},{"slug":"pipe-flow-velocity-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/pipe-flow-velocity-calculator/","title":"Pipe flow velocity calculator (GPM to ft/s)","short_title":"Pipe velocity calculator","dek":"Find water velocity in a pipe from the flow rate: V = 0.4085 x GPM / diameter squared, in feet per second.","intro":"Water velocity is the number that decides whether a pipe is sized right, and it falls out of the flow and the bore. The velocity in feet per second equals 0.4085 times the flow in gallons per minute divided by the inside diameter in inches squared. Enter the flow and the inside diameter to get the velocity. Velocity matters in both directions: too slow and sediment settles and the line fouls, too fast and you get noise, erosion of the pipe wall, and water hammer that can split fittings. Most systems are designed to roughly 2 to 8 feet per second, with tighter limits where quiet operation or erosion resistance matters, often around 5 feet per second for cold water and 3 for hot in copper. Use the actual inside diameter for the pipe material and schedule, not the nominal size, and confirm the velocity limit against the plumbing or piping code, the manufacturer, and the application."},{"slug":"pipe-volume-capacity-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/pipe-volume-capacity-calculator/","title":"Pipe volume calculator (gallons of water)","short_title":"Pipe volume calculator","dek":"Find the water a pipe holds from its inside diameter and length: V = pi/4 x diameter squared x length, in gallons.","intro":"Knowing how much water a run of pipe holds is the starting point for sizing a flush, mixing a glycol charge, dosing chlorination, or estimating the water to drain down a system. The volume is the area of the bore times the length: pi divided by four, times the inside diameter squared, times the length, converted to gallons at 7.48 gallons per cubic foot. Enter the inside diameter in inches and the length in feet. Use the actual inside diameter for the pipe material and schedule, not the nominal size, because the nominal call-out is not the real bore and the difference adds up over a long run. For a whole-system volume, add the fittings, the water heater or storage tank, and any vessels or coils on the loop."},{"slug":"propane-tank-runtime-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/propane-tank-runtime-calculator/","title":"Propane tank runtime calculator","short_title":"Propane runtime calculator","dek":"Find how long a propane tank lasts: hours = usable tank energy divided by the appliance BTU load.","intro":"Knowing how long a propane tank lasts drives the refill schedule and whether a tank can even keep up with a burner, and the math is the usable tank energy divided by the appliance load. The energy is the tank gallons times about 91,500 BTU per gallon times the usable fraction. Enter the tank size in gallons, the appliance load in BTU per hour, and the usable percent. Common sizes help: a 20-pound grill cylinder holds about 4.6 gallons, a 100-pound cylinder about 23.6 gallons, and a 500-gallon tank is filled to roughly 400. Two real-world limits shape the answer. A tank is only filled to about 80 percent to leave room for the liquid to expand, so the usable amount is less than the nominal size. And in cold weather the liquid propane vaporizes more slowly, so a small cylinder cannot supply a large burner continuously, frosting up and starving the appliance well before it is empty, which is a sizing problem the runtime number alone does not show. Use this for planning refills and sanity-checking tank size, and confirm the tank, the regulator, the cold-weather vaporization rate, and the appliance BTU draw with the propane supplier."},{"slug":"pue-data-center-calculator","trade":"datacenter","url":"https://anvilfield.com/calculators/pue-data-center-calculator/","title":"PUE calculator (data center efficiency)","short_title":"PUE calculator","dek":"Find a data center's Power Usage Effectiveness: total facility power divided by the IT load, plus DCiE and the overhead in kW.","intro":"Power Usage Effectiveness is the standard measure of how much of a data center's electricity actually reaches the computing equipment. It is the total facility power divided by the IT equipment power. A PUE of 1.0 would mean every watt drawn from the utility lands on the servers, storage, and network gear; real facilities run higher because cooling, UPS and transformer losses, and lighting all consume power that never reaches the IT load. Enter the total facility power and the IT load in the same unit (kW) and the calculator returns the PUE, the DCiE (the inverse, as a percentage), and the overhead in kW. Use it to benchmark a room, to size the gap between what you pay for and what you compute with, or to check the payoff of an efficiency project such as containment or an economizer. Treat the result as a snapshot: a defensible, comparable PUE is built from metered annualized energy in kWh measured at agreed points, not a single instantaneous reading, and the climate and load factor move the number."},{"slug":"pump-brake-horsepower-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/pump-brake-horsepower-calculator/","title":"Pump brake horsepower calculator (BHP)","short_title":"Pump BHP calculator","dek":"Find pump brake horsepower from flow and head: BHP = (gpm x head x specific gravity) / (3960 x efficiency).","intro":"Sizing a pump and its motor starts with the brake horsepower, the power the pump shaft actually demands. The formula is BHP = (gpm x total head x specific gravity) / (3960 x pump efficiency). Enter the flow in gallons per minute, the total dynamic head in feet (the static lift plus the friction losses through the pipe and fittings, not just the vertical rise), the pump efficiency as a percent (often 60 to 80), and the fluid specific gravity (1.0 for water, higher for denser fluids). The tool returns both the water horsepower, which is the useful hydraulic work, and the brake horsepower, which is larger because no pump is perfectly efficient. The motor is then sized above the brake horsepower, using the motor service factor or stepping up to the next standard size so it is not loaded to its limit. Read the brake horsepower against the manufacturer pump curve at the actual operating point, since efficiency changes along the curve, and confirm the head calculation, the curve, and the final motor selection with the manufacturer and the engineer."},{"slug":"rack-cooling-airflow-cfm-calculator","trade":"datacenter","url":"https://anvilfield.com/calculators/rack-cooling-airflow-cfm-calculator/","title":"Rack cooling airflow (CFM) calculator","short_title":"Rack airflow CFM calculator","dek":"Find the CFM a rack needs from its kW load and the supply-to-return temperature rise: CFM = kW x 3412 / (1.08 x deltaT).","intro":"A rack rejects its entire electrical load as heat, and the cooling system has to move enough air through it to carry that heat away at the design temperature rise. This calculator uses the sensible-heat airflow relationship, CFM = kW x 3412 / (1.08 x delta-T), where delta-T is the difference between the cold supply air at the inlet and the hot return leaving the rack. Enter the rack IT load in kilowatts and the design delta-T, commonly 15 to 25 degrees Fahrenheit. A higher delta-T carries the same heat with less air, which is why hot-aisle containment (raising the return temperature) cuts fan energy; a lower delta-T needs more air. The 1.08 constant assumes standard-density air at sea level and moderate temperature and drops at altitude and high temperature, so a hot or high-elevation site needs more CFM than the formula shows. Use this as a per-rack sanity check for hot-aisle/cold-aisle layout and containment, and confirm the design delta-T and airflow with the mechanical engineer."},{"slug":"rack-pdu-current-sizing-calculator","trade":"datacenter","url":"https://anvilfield.com/calculators/rack-pdu-current-sizing-calculator/","title":"Rack and PDU current (amps) and 80% sizing calculator","short_title":"Rack current & sizing calculator","dek":"Convert rack kW to amps (single or three phase) and size the continuous feeder and breaker at 80% per the NEC.","intro":"Data center IT load runs continuously, so the current draw and the circuit that feeds it are two different numbers. This calculator converts a rack or PDU load in kilowatts to running amps, using three-phase amps = kW x 1000 / (sqrt3 x V x PF) or single-phase amps = kW x 1000 / (V x PF), then applies the NEC continuous-load rule. Enter the load in kW, the voltage (commonly 208 V or 415/400 V three-phase in the white space), the phase, and the power factor (modern server power supplies run near 1.0). Because the load is on for three hours or more, the NEC treats it as continuous and limits it to 80 percent of the branch-circuit or feeder rating, so the conductor and overcurrent device are sized for at least the draw divided by 0.8. Remember redundancy: A and B feeds each have to carry the full rack when the other path drops, so size each feed for the whole load and run each near half its rating in normal operation. Confirm the voltage, power factor, conductor derating, and overcurrent selection with the electrical engineer and the NEC."},{"slug":"raised-floor-load-calculator","trade":"datacenter","url":"https://anvilfield.com/calculators/raised-floor-load-calculator/","title":"Raised access floor load calculator","short_title":"Raised floor load calculator","dek":"Check the uniform load a cabinet puts on a raised access floor (psf) against the floor rating before you roll it into place.","intro":"A raised access floor carries the racks, and a fully loaded cabinet is heavy enough to overload a floor that was not specified for it. This calculator computes the uniform load, pressure (psf) = loaded weight / footprint area, from the equipment weight and its footprint. Enter the fully loaded weight (a dense cabinet runs 2,000 to 3,000 pounds or more), the footprint length and width in inches, and optionally the floor system rated uniform capacity to check against. The uniform number is only one of three limits, though: a raised access floor is also rated for concentrated load (a heavy point load on a small area at the weakest part of a tile) and rolling load (a caster wheel rolling a loaded cabinet across the tiles during the move-in), and the rolling or concentrated case usually governs when heavy gear is installed. Plan the delivery path, use load-spreading plates for the move, and confirm the tile, stringer, and pedestal ratings with the floor manufacturer and the structural engineer."},{"slug":"rational-method-runoff-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/rational-method-runoff-calculator/","title":"Rational method runoff calculator (Q = CiA)","short_title":"Runoff calculator (Q=CiA)","dek":"Estimate peak stormwater runoff from a small site with the rational method: Q = C x i x A, in cubic feet per second.","intro":"The rational method is the most common way to estimate the peak rate of stormwater runoff from a small drainage area, and it is the starting point for sizing swales, inlets, pipes, and detention. The formula is Q = C x i x A: Q is the peak flow in cubic feet per second, C is the runoff coefficient (the fraction of rain that runs off instead of soaking in, roughly 0.10 to 0.30 for lawns and open ground and 0.70 to 0.95 for pavement and roofs), i is the rainfall intensity in inches per hour for the design storm at the site time of concentration, and A is the drainage area in acres. It works cleanly in these units because one acre-inch per hour is almost exactly one cfs. Enter the three values to get the peak flow. Treat the result as a planning estimate for small sites: the runoff coefficient, the design storm and its intensity, the time of concentration, and whether the rational method is even accepted are all set by the local stormwater code and the civil engineer, and a composite C is needed when the area mixes surfaces."},{"slug":"rebar-weight-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/rebar-weight-calculator/","title":"Rebar weight calculator","short_title":"Rebar weight calculator","dek":"Estimate the weight of reinforcing steel in pounds and tons from the bar size, the length per bar, and the number of bars, using the standard ASTM A615 unit weights.","intro":"Pick the reinforcing bar size, enter the length of one bar in feet, and enter how many bars of that size you have. The calculator multiplies the total linear feet by the nominal ASTM A615 unit weight for that bar (for example, a #5 bar weighs 1.043 lb per foot) and returns the weight in pounds and tons. Run it once per bar size and add the results for the full mat or member. Add for lap splices, waste, and the chairs and tie wire, and confirm the mill weight on the bar tag before you place the order."},{"slug":"retaining-wall-block-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/retaining-wall-block-calculator/","title":"Retaining wall block calculator (segmental wall)","short_title":"Retaining wall calculator","dek":"Find the segmental wall blocks for a wall: face blocks = wall face area divided by the block face area.","intro":"Estimating a segmental retaining wall starts with the face blocks: the wall face area, length times height, divided by the face area of one block, plus a small waste allowance. Enter the wall length and height in feet and the block face area in square feet. A common SRW unit shows roughly half a square foot of face, but it varies widely by product, so use the manufacturer's figure for the block you are setting. The result is the face units only, and a wall is more than its face. Budget for a cap course to finish the top, a buried base course set below grade on a compacted aggregate leveling pad, geogrid soil-reinforcement layers tied back into the retained soil at the spacing the design calls for, and drainage stone with a perforated pipe behind the wall. Two things are not optional: the base preparation and the drainage are what make the wall last, and a segmental wall taller than about four feet, with the exact trigger set locally, generally requires an engineered design with geogrid. Confirm the block, the geogrid schedule, the height limit, and the drainage with the manufacturer and the engineer."},{"slug":"roof-squares-pitch-calculator","trade":"roofing","url":"https://anvilfield.com/calculators/roof-squares-pitch-calculator/","title":"Roofing squares calculator (footprint + pitch)","short_title":"Roof squares calculator","dek":"Estimate roofing squares from the building footprint and the pitch: roof area = footprint x the pitch multiplier, and one square is 100 square feet.","intro":"A roof is bigger than the building under it, because the slope stretches the area. This calculator converts a flat plan footprint into actual roof area and roofing squares using the pitch multiplier, the slope factor for a given rise per 12 inches of run. Roof area equals the footprint times that multiplier, and one roofing square is 100 square feet. Enter the footprint area in square feet, the pitch as rise per 12, and a waste percentage to cover cuts, hips, valleys, starter, and ridge. The result is a solid estimate for the main field of a simple gable or hip roof from a flat footprint. On a cut-up roof with multiple planes, dormers, and long valleys, measure each plane and add the waste and accessory courses separately, and confirm coverage against the shingle or panel manufacturer."},{"slug":"sensible-heat-airflow-btu-calculator","trade":"hvac","url":"https://anvilfield.com/calculators/sensible-heat-airflow-btu-calculator/","title":"Sensible heat calculator (1.08 x CFM x delta-T)","short_title":"Sensible heat calculator","dek":"Find the sensible heat an airstream carries: BTU/hr = 1.08 x CFM x the temperature difference.","intro":"The sensible heat equation is one of the most-used relationships in HVAC, tying airflow and temperature to heat. The sensible heat in BTU per hour equals 1.08 times the airflow in CFM times the temperature difference in degrees Fahrenheit. Enter the CFM and the delta-T (supply to return, or across a coil) to get the BTU/hr and the equivalent tons at 12,000 BTU/hr per ton. The 1.08 constant is for standard air at sea level and combines air density with its specific heat, so it shifts with altitude, temperature, and humidity. This is the sensible (dry, temperature-change) heat only; the latent heat that removes moisture from the air is a separate calculation, which is why a coil's total capacity is more than this number in a humid space. Use it to check whether the airflow matches the load, to estimate the heat a duct delivers, or to run a quick delta-T diagnostic on a system, and confirm equipment selection against a full Manual J load calculation."},{"slug":"single-phase-watts-to-amps-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/single-phase-watts-to-amps-calculator/","title":"Single-phase amps calculator (watts to amps)","short_title":"Watts to amps calculator","dek":"Find single-phase current from power: amps = watts divided by (volts x power factor).","intro":"Converting power to current is one of the most common electrical field calculations, and for a single-phase load it is straightforward: amps equal watts divided by the voltage times the power factor. Enter the power in watts, the line voltage (commonly 120, 208, or 240 for single-phase), and the power factor. Power factor is 1.0 for purely resistive loads like electric heat and incandescent lighting, and lower (often 0.8 to 0.95) for motors and electronic loads that draw reactive current. This is the single-phase relationship; a three-phase load divides further by the square root of three. Use the actual running watts rather than a nameplate maximum, and the real voltage at the load. The result is the load current only: size the conductor and the overcurrent device per the NEC, which adds the 125 percent rule for continuous loads and any derating for temperature and conductor bundling. For a quick reverse check, watts equal amps times volts times power factor."},{"slug":"slope-grade-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/slope-grade-calculator/","title":"Slope and grade calculator","short_title":"Slope and grade calculator","dek":"Turn rise and run into percent grade, degrees, a run-to-rise ratio, and inches per foot for grading, drainage, and ramps.","intro":"Enter rise and run in the same units and the calculator returns the percent grade, the angle in degrees, the run-to-rise ratio, and the equivalent inches per foot. Use it to check site drainage, a ramp, a swale, or a parking slope, then confirm the number against the governing code."},{"slug":"sod-seed-coverage-calculator","trade":"landscaping","url":"https://anvilfield.com/calculators/sod-seed-coverage-calculator/","title":"Sod and seed coverage calculator","short_title":"Sod & seed calculator","dek":"Find the sod (square feet and pallets) or grass seed (pounds) to cover an area.","intro":"Whether you sod or seed, the estimate starts with the area to cover. For sod, the square footage needed is the area plus a waste allowance for cuts around beds and curves, converted to pallets, where a pallet commonly covers about 450 square feet, though it varies by farm. For seed, the quantity is the area in thousands of square feet times the seeding rate in pounds per 1000 square feet. Enter the area, the waste percent, the pallet coverage, and the seeding rate. The seeding rate is the number that swings most: it varies widely by species and by whether this is a new lawn or an overseed, from a couple of pounds to ten or more per 1000 square feet, so use the rate printed on the bag rather than a single default. The result either way is only as good as the soil preparation underneath it, because the grade, the amendment, a loosened seedbed, and firm soil contact are what actually establish a lawn, not the quantity of sod or seed. Confirm the variety, the seeding rate, and the soil amendment with the supplier and a soil test."},{"slug":"soil-excavation-swell-shrink-calculator","trade":"paving","url":"https://anvilfield.com/calculators/soil-excavation-swell-shrink-calculator/","title":"Soil swell and shrink calculator (excavation volume)","short_title":"Soil swell/shrink calculator","dek":"Convert earthwork volume between bank, loose (haul), and compacted using swell and shrink: loose = bank x (1+swell), compacted = bank x (1-shrink).","intro":"Dirt changes volume depending on its state, and getting that wrong throws off both the truck count and the fill. Soil in the ground is measured in bank cubic yards (BCY). Once you dig it, it loosens and takes up more room, measured in loose cubic yards (LCY), which is what you actually haul. Placed and compacted in a fill, it settles to less than its bank volume, measured in compacted cubic yards (CCY). Loose equals bank times one plus the swell percentage; compacted equals bank times one minus the shrink percentage. Enter the bank volume and the swell and shrink percentages for your soil. Swell and shrink vary widely by soil type and moisture, with sand, clay, and rock behaving very differently, so base a real estimate on load counts, compaction tests, or the geotechnical report rather than rule-of-thumb factors."},{"slug":"solar-pv-production-estimate-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/solar-pv-production-estimate-calculator/","title":"Solar PV production calculator (kWh estimate)","short_title":"Solar production calculator","dek":"Estimate solar energy: kWh = system kW x peak sun hours x a derate factor, per day and per year.","intro":"This calculator gives a quick estimate of how much energy a solar array will make, the starting point for sizing a system, checking a proposal, or sanity-testing a payback. The energy equals the system size in kilowatts DC times the peak sun hours per day times a derate factor, multiplied by 365 for the year. Enter the system size, the site peak sun hours, and a derate percentage. The derate, commonly about 75 to 85 percent, is where the real-world losses live: inverter efficiency, high-temperature derating of the panels, soiling, wiring and mismatch losses, and any shading, so the AC energy delivered is always less than the nameplate DC times sun hours. Peak sun hours are not daylight hours; they are the equivalent hours of full-sun irradiance and they vary by location, tilt, orientation, and season. For a number you can put in a proposal, pull the site's real solar resource from a tool like NREL PVWatts and use a modeled derate rather than an assumed one."},{"slug":"sonotube-pier-concrete-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/sonotube-pier-concrete-calculator/","title":"Sonotube pier concrete calculator (round column)","short_title":"Sonotube concrete calculator","dek":"Find the concrete for round piers or columns: volume = pi x radius squared x height.","intro":"Round piers and columns formed with cardboard tubes need their concrete figured as a cylinder, and the volume is pi times the radius squared times the height. Enter the tube diameter in inches, the height or depth in feet, and the number of piers, and the tool returns the total in cubic feet and cubic yards plus an approximate bag count, using about 0.6 cubic foot per 80-pound bag and 0.45 per 60-pound bag. This is the straight cylinder volume, so add concrete for over-excavation, for a belled or flared footing at the base, and for waste, and round up. The economics shift with quantity: bagged concrete is fine for one or two small piers, but past a few it is usually cheaper and far faster to order ready-mixed by the yard. The pier diameter and depth are not a rule of thumb either, they are set by the load the pier carries, the bearing capacity of the soil, and the local frost depth, since a footing above the frost line heaves. Confirm the pier size, the depth, and any reinforcement with the structural engineer and the geotechnical report."},{"slug":"stair-rise-run-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/stair-rise-run-calculator/","title":"Stair rise and run calculator (riser height)","short_title":"Stair calculator","dek":"Lay out a stair from the total rise: number of equal risers, the exact riser height, the tread count, and the total run.","intro":"A safe, comfortable, code-legal stair starts with dividing the total rise into equal risers. This calculator takes the total rise (finished floor to finished floor), divides it by a target riser height near the comfortable range, rounds to a whole number of risers, then gives the exact riser height so every step is equal, plus the tread count (one fewer than the risers) and the total horizontal run from your tread depth. Enter the total rise in inches, a target riser, and a tread depth. Equal risers are not optional: an odd step out of the pattern is a trip hazard and a code violation. The maximum riser, minimum tread, the allowed variation between risers, headroom, and nosing are all set by the IRC or IBC and the local amendments, so confirm the layout and the rise-plus-run or 2R+T comfort rule against the adopted code and the AHJ before you cut stringers or set forms."},{"slug":"tank-fill-drain-time-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/tank-fill-drain-time-calculator/","title":"Tank fill and drain time calculator","short_title":"Fill/drain time calculator","dek":"Find how long a tank takes to fill or empty: time = volume divided by flow rate.","intro":"Knowing how long a tank, basin, or pool takes to fill or empty drives the pump sizing, the schedule, and the operator's plan, and the basic relationship is simple: time equals volume divided by flow rate. Enter the volume in gallons and the flow in gallons per minute to get the minutes and hours. The estimate assumes a steady flow, which holds well for a pump running at a fixed rate, but two real-world effects make a gravity system slower than the constant-rate figure. A gravity drain loses head as the level drops, so it runs fast at first and slows toward the end, taking longer than a single average rate suggests. And a pump does not hold one flow either; it moves along its performance curve as the head changes, so the delivered flow at the real operating point is what counts, not the nameplate maximum. For sizing a fill cycle or a pump-down, use the actual delivered flow and add margin for the slowdown. Confirm the pump selection, the drain sizing, and any code-required fill or drain time with the manufacturer and the engineer."},{"slug":"tank-volume-cylindrical-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/tank-volume-cylindrical-calculator/","title":"Tank volume calculator (cylindrical, gallons)","short_title":"Tank volume calculator","dek":"Find the gallons in a vertical cylindrical tank from its diameter and height: V = pi/4 x diameter squared x height, in gallons.","intro":"Sizing a cistern, a storage or buffer tank, or a chemical vessel starts with how much it actually holds. For a straight vertical cylinder the volume is pi divided by four, times the diameter squared, times the height, converted to gallons at 7.48 gallons per cubic foot. Enter the diameter and height in feet and a fill level percentage to get both the full capacity and the volume at the working level. This formula is for a vertical cylinder; a horizontal cylindrical tank, or one with dished or coned heads, needs a different calculation, and the usable volume is always less than the raw geometric volume once you subtract the outlet height, the freeboard, and any dead space below the draw. Confirm the tank geometry and the real working level before you rely on a number for a fill, a flush, or a chemical charge."},{"slug":"thermal-pipe-expansion-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/thermal-pipe-expansion-calculator/","title":"Thermal pipe expansion calculator (movement)","short_title":"Pipe expansion calculator","dek":"Find how much a pipe run grows or shrinks: movement = length x coefficient x temperature change.","intro":"Pipe grows when it heats and shrinks when it cools, and on a long run that movement is large enough to buckle the pipe or tear the joints if it is not planned for. The movement is length times the coefficient of thermal expansion times the temperature change. Enter the run length in feet, the temperature swing in degrees Fahrenheit (from the coldest to the hottest the line will see in service), and the material coefficient in millionths of an inch per inch per degree F. Typical coefficients are about 6.5 for carbon steel, 9.6 for stainless, 9.8 for copper, 30 for PVC, 34 for CPVC, and 80 for PEX, which is why plastic piping moves several times more than steel for the same temperature change. The result is how far the run expands or contracts, and that movement has to be absorbed by expansion loops, offsets, or expansion joints, with the pipe correctly anchored and guided so the growth is directed and not fought. Treat this as a planning estimate and confirm the coefficient, the design temperature range, and the flexibility or stress design with the manufacturer and the engineer."},{"slug":"three-phase-power-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/three-phase-power-calculator/","title":"Three-phase power calculator (kW, kVA, amps)","short_title":"Three-phase power calculator","dek":"Find three-phase kW and kVA from volts, amps, and power factor: kVA = sqrt(3) x V x A / 1000, and kW = kVA x PF.","intro":"Three-phase power ties together voltage, current, and power factor, and the field needs to move between them constantly to size a service, check a load, or read a nameplate. Apparent power in kVA equals the square root of three times the line-to-line voltage times the line current, divided by 1000, and real power in kW equals that kVA times the power factor. Enter the line-to-line voltage (208, 240, 480, or 600 are common), the line current in amps, and the power factor, which is 1.0 for a resistive load and lower for motors and other inductive loads. To go the other way and solve current from a known kW load, amps equals kW times 1000 divided by the square root of three, the voltage, and the power factor. These are the core relationships; use the equipment nameplate and the real power factor, and apply NEC conductor sizing, continuous-load, and derating rules to the actual installation."},{"slug":"trench-excavation-volume-calculator","trade":"paving","url":"https://anvilfield.com/calculators/trench-excavation-volume-calculator/","title":"Trench excavation volume calculator (cubic yards)","short_title":"Trench volume calculator","dek":"Find excavation volume: length x width x depth in feet, divided by 27 for cubic yards, plus an approximate truck-load count.","intro":"Estimating a dig starts with the volume of soil to move. Length times width times depth in feet gives cubic feet, divided by 27 gives cubic yards, and divided by the truck capacity gives an approximate number of haul loads. Enter the three dimensions and a truck size. The number this gives is the bank volume, the soil in place before you dig it, which matters because excavated soil swells, commonly 15 to 30 percent depending on the soil, so the loose volume you actually load and haul is larger, and soil placed back as fill compacts to less than its bank volume. For real truck counts and backfill quantities, run the bank volume through a swell and shrink conversion. This is a simple prism estimate for a straight trench or a rectangular cut; sloped or benched excavation walls, required for stability, add volume beyond the neat line. Remember that an excavation 5 feet deep or more generally requires an OSHA protective system, which is a safety requirement, not an option."},{"slug":"ups-redundancy-capacity-calculator","trade":"datacenter","url":"https://anvilfield.com/calculators/ups-redundancy-capacity-calculator/","title":"UPS redundancy capacity calculator (N+1, 2N)","short_title":"Redundancy capacity calculator","dek":"Find the usable capacity of a UPS, generator, or cooling plant under N, N+1, or 2N, and check it carries the critical load with a unit down.","intro":"Installed capacity and usable capacity are not the same once redundancy is required, and the usable number is the one that keeps the load up when a module fails or is pulled for maintenance. This calculator computes usable capacity for a UPS, generator, or cooling plant: for N there is no spare, so usable = modules x per-module kW; for N+1 one module is reserved, so usable = (modules - 1) x kW; for 2N the plant is two independent full systems, so usable = half the modules x kW. Enter the per-module capacity, the number installed, the topology, and optionally the critical load to check whether it is still carried with a unit out. Redundancy is about surviving a fault or a concurrent-maintenance event, and true concurrent maintainability and fault tolerance depend on the entire power path (utility feeds, switchgear, PDUs, and the A/B distribution), not the module count alone, so read this alongside the one-line diagram and the Uptime Institute tier target. Confirm the topology and the module ratings with the electrical engineer."},{"slug":"voltage-drop-calculator","trade":"electrical","url":"https://anvilfield.com/calculators/voltage-drop-calculator/","title":"Voltage drop calculator","short_title":"Voltage drop calculator","dek":"Size the conductor against the run: enter the load and length, get the volts dropped and the percent against the 3 percent target.","intro":"Enter the system, the load current, the one-way routed length, and the conductor. The result is the volts dropped and the percent of source voltage, with a quick read against the common 3 percent branch target. Use the routed length and 125 percent of a continuous load for the honest number."},{"slug":"wall-stud-count-calculator","trade":"concrete","url":"https://anvilfield.com/calculators/wall-stud-count-calculator/","title":"Wall stud count calculator (framing)","short_title":"Stud count calculator","dek":"Find how many studs a wall needs: length divided by the on-center spacing, plus the corners and openings.","intro":"Framing a wall starts with the stud count, and the math is the wall length in inches divided by the on-center spacing, plus one stud to close the end. Enter the wall length in feet, the spacing in inches (16 and 24 on center are the standards), and an allowance for the extras. The straight spacing formula gives the field studs in a plain wall, but a real wall always needs more, and that is where estimates go wrong: every corner and wall intersection takes extra studs, and every door and window needs king, jack, and cripple studs framing the opening, on top of cut waste. A 10 to 15 percent add covers a typical wall, and a cut-up wall with many openings needs more. This counts the vertical studs only, so order the top and bottom plates separately by the linear foot, doubling the top plate where required, and add the headers, blocking, and fire-blocking. The same math works for wood or light-gauge metal studs. Confirm the spacing, the header sizing, and any shear-wall stud and nailing requirements against the plans and the engineer."},{"slug":"water-heating-btu-rate-calculator","trade":"plumbing","url":"https://anvilfield.com/calculators/water-heating-btu-rate-calculator/","title":"Water heating BTU calculator (GPM x 500 x rise)","short_title":"Water heating calculator","dek":"Find the heat to warm flowing water: BTU/hr = GPM x 500 x the temperature rise, with the kW equivalent.","intro":"Sizing a water heater, a booster, or a recirculation load comes down to the heat needed to raise a flow of water a certain number of degrees. The rate in BTU per hour equals the flow in gallons per minute times 500 times the temperature rise in degrees Fahrenheit. Enter the flow and the rise from incoming cold to delivered hot. The 500 constant is specific to water: 8.33 pounds per gallon, times 60 minutes per hour, times 1 BTU per pound per degree. The result is the energy to heat a continuous flow, which is exactly how you size an instantaneous or tankless heater, an electric booster (shown here in kW), or a recirculation system. A storage tank heater is different: it can briefly deliver more hot water than its burner or element can heat by drawing the tank down, so a tank type is sized to the peak demand and the recovery rate together, not to the instantaneous rate alone. Use the real incoming water temperature for the season, and confirm the selection against the manufacturer and the fixture load."}]}