Concrete Footing Calculator
Concrete for footings & foundation trenches
Pouring strip footings or a foundation trench? Enter the footing length, width and depth to get the concrete required in cubic yards and bags.
Sizing a footing
Treat the footing as a long box: length × width × depth. For multiple identical footings, set the "number of areas" field. Local codes dictate minimum footing size, so always check before you dig.
Don't run short
Footings are structural — a cold joint from running out mid-pour is a real problem. Order 10% extra.
Width, depth and rebar
A common residential footing is about twice the width of the wall it supports and at least as deep as it is wide, but your local code and soil set the real minimums. Most footings need two runs of rebar along their length. Keep the trench bottom flat, firm and undisturbed — footings should bear on solid ground, never loose backfill.
Concrete Footing Calculator: frequently asked questions
How deep should a footing be?
Below the local frost line — often 12–48 inches depending on climate. Check your building code.
Bags or ready-mix for footings?
Small post footings can be bagged; continuous foundation footings are almost always ready-mix.
How wide should a footing be?
A rule of thumb is twice the wall thickness (e.g., 16 inches for an 8-inch wall), but the required width depends on the load and soil bearing capacity — always follow your local building code.