Concrete Footing Calculator
Calculate concrete for footings by the linear foot.
Enter the total length of your footing trench along with its width and depth to get the concrete volume in cubic yards and cubic feet, plus the number of 80-lb bags. A waste allowance covers over-excavation and uneven trench bottoms.
How it works
Footing volume is length × width × depth, converted to feet and divided by 27 for cubic yards. Footings are often wider and deeper than slabs, and trench bottoms are rarely perfectly even, so a 10% allowance is sensible.
Frequently asked questions
How much concrete do I need for footings?
Multiply footing length by its width and depth (in feet) and divide by 27 for cubic yards. A 40-ft footing 16 inches wide and 8 inches deep is about 1.45 cubic yards with waste.
Should footings be poured separately from the slab?
Often yes for frost-protected or load-bearing footings, though monolithic pours combine footing and slab in one. Follow your local code and plans.
How much extra concrete should I order for footings?
Around 10% — trench bottoms are uneven and over-excavation is common.
Is this calculator free and private?
Yes. Every CubicCabin calculator runs entirely in your browser, so the numbers you enter are never uploaded or stored. There's no sign-up, no limits, and it keeps working even if you lose connection after the page loads.