Strip Footing Concrete Calculator
Estimate concrete for a continuous strip (wall) footing from its total run, width and depth — cubic yards and 60/80 lb bags.
How it works
cubic feet = run(ft) × (width ÷ 12) × (depth ÷ 12) · cubic yards = cubic feet ÷ 27
A strip footing is one long trench of concrete under a wall, so its volume is simply the total run measured in feet times the cross-section, whose width and depth are in inches and therefore divided by 12. Add the corners into the run only once. Bag counts come from each bag’s yield: about 0.45 cu ft for a 60 lb bag and 0.60 cu ft for an 80 lb bag.
Worked example
A 100 ft foundation footing 18 in wide and 10 in deep: 100 × 1.5 × 0.833 = 125 cu ft, ÷ 27 = 4.63 cubic yards — clearly a ready-mix job, since that is over 200 eighty-pound bags.
Frequently asked questions
How wide should a strip footing be?
Commonly twice the wall thickness and never less than the wall itself — often 16–24 in for house foundations. The real width depends on the soil’s bearing capacity and the load above, so it is a code and engineering question.
How do I handle corners and steps?
Measure the run along the centreline of the trench so each corner is counted once, not twice. Where a footing steps down a slope, add each level’s length; keep the step no steeper than the code allows (often 1 vertical to 2 horizontal).
Do strip footings need rebar?
Most codes require two or more continuous horizontal bars near the bottom, lapped at splices and bent around corners. Rebar does not change the concrete volume but is usually mandatory for inspection.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.