Concrete footing calculator
Estimate the material for a rectangular footing or trench from its finished dimensions.
Enter footing dimensions
Footing volume formula
Length × width × depth gives cubic feet when all three dimensions are in feet. Divide depth in inches by 12 first, then divide cubic feet by 27 to get cubic yards. For several identical footings, multiply by quantity.
Formula: length ft × width ft × (depth in ÷ 12) × quantity ÷ 27 = exact yd³.
Worked example: 20 ft long, 2 ft wide, 12 in deep
20 × 2 × 1 = 40 ft³, or 1.48 yd³ exact. With 10% extra, plan for 44 ft³ or 1.63 yd³. At 0.60 ft³ per 80 lb bag, this would take 74 bags. A supplier may have a minimum delivery quantity.
Measure the excavation you will actually fill
Over-excavation, uneven sides and changes in depth increase volume. Measure the finished trench, not only the drawing. Structural footing dimensions and reinforcement depend on site conditions and local requirements; the calculator does not design them.
Questions people ask
Is this for round piers?
This page is for rectangular footings. Use the multi-pour calculator and choose “Round column / hole” for cylindrical piers.
Why is the order amount larger than exact volume?
The order result applies the extra percentage you entered. It is separate from the geometric volume.
Content and calculator by pourmeasure. Formula and assumption notes: methodology and sources. Updated October 2026. No independent engineering review is claimed.