Field calculator
Footing bearing pressure calculator (soil)
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.
Result
Footing bearing pressure: pressure = load divided by footing area (q = P / (L × W)). Enter the service load in pounds and the footing length and width in feet, and optionally the allowable soil bearing pressure to check it. The result is the pressure the footing puts on the soil, compared against the allowable bearing capacity from the geotechnical report. If the pressure exceeds the allowable, the footing must be enlarged or the load reduced. Two cautions: this is a quick service-load check, not a footing design, so the allowable bearing value must come from the geotech, not a guess; and the actual footing design (the reinforcement, the punching-shear and one-way shear checks, the settlement, and the load combinations) is the structural engineer's work. Use this to size or sanity-check a footing and confirm everything with the geotechnical engineer and the structural engineer of record.
anvilfield.com/calculators/footing-bearing-pressure-calculator · Free field calculators and FieldOS. A planning estimate, verify against the code, the manufacturer, and the engineer of record.
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Bearing pressure FAQ
What is a footing?
A footing is the part of a foundation that bears directly on the soil and spreads a building's load over enough ground to keep the soil from overloading. A spread footing sits under a column, a strip footing under a wall. Its size comes from the load divided by the soil's allowable bearing capacity.
What is the difference between a shallow and a deep foundation?
A shallow foundation bears near the surface and spreads load into soil that is strong close to grade, using spread, strip, or mat footings. A deep foundation uses piles or drilled piers to carry the load down through weak soil to a firm layer. The soils report decides which the site needs.
How deep should a footing be?
A footing has to bear on firm soil, below the local frost line, and at least 12 in below undisturbed ground under the IBC and IRC. The frost line is regional, from about a foot in the south to 4 ft or more up north. A frost-protected shallow foundation can sit shallower with perimeter insulation.
What is a spread footing?
A spread footing, also called an isolated or pad footing, is a concrete pad under a column that spreads its point load over the soil. Its plan area is the service load divided by the allowable bearing pressure, and its thickness and bottom steel are sized for shear and bending under ACI 318.
How big does a footing need to be?
A footing's bearing area is the service load divided by the soil's allowable bearing capacity. A 60,000 lb column on 3,000 psf soil needs about 20 square feet, so roughly a 4 ft 6 in square pad. The soils report sets the bearing value, and the engineer sets the thickness and reinforcement.