How a continuous footing is measured
A strip footing is a simple rectangular prism: length × width × depth ÷ 12 gives cubic feet, ÷ 27 gives cubic yards. Standard residential footings pour 16–20 inches wide and 6–8 inches deep under load-bearing walls, widening to spread the wall's weight over more soil.
Before you dig
Call 811 before digging — utility marking is free and legally required in most states. The footing bottom must sit on undisturbed or compacted soil below the frost line; soft spots should be cut out and filled with extra concrete, which is exactly why ordering 10% more than the calculated volume is standard practice.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- ASTM International — C94 for ready-mixed concrete, C150 for cement and C143 for slump testing.
- American Concrete Institute — ACI 318 code requirements and ACI 302 slab construction guidance.
- Portland Cement Association — mix design, yield and curing data published by the US cement industry.
Figures, formulas and reference tables last verified: 19 September 2026.