Supply MathConcrete for common footing runs (+10%)
| Length | Width × depth | Cubic yards | 80 lb bags |
|---|---|---|---|
| 20 ft | 12 × 8 in | 0.54 | 25 |
| 20 ft | 16 × 8 in | 0.72 | 33 |
| 40 ft | 16 × 8 in | 1.45 | 66 |
| 40 ft | 20 × 10 in | 2.26 | 102 |
| 60 ft | 20 × 10 in | 3.4 | 153 |
| 100 ft | 20 × 12 in | 6.79 | 306 |
Structural footings must follow your local building code and frost depth. This tool only estimates material.
Frequently asked questions
How do I calculate concrete for a footing?
Multiply footing length × width × depth in feet, then divide by 27 for cubic yards. A 40 ft footing that is 16 in wide and 8 in deep is 40 × 1.333 × 0.667 = 35.6 ft³, about 1.32 yd³ before waste.
How wide and deep should a footing be?
It depends on the load, soil and frost depth set by your local building code. Footings for light walls are often about twice the wall width and at least 6–8 in thick, but follow your plans or local code.