Concrete Footing Calculator
Continuous strip footings for foundations, garages, and additions: total run length and the footing cross-section in, cubic yards out. Decimals welcome throughout.
Common footing sections, per 10 ft of run
| Section (W × D) | Typical wall above | Cu yd per 10 ft |
|---|---|---|
| 12" × 6" | 4" wall / light | 0.19 |
| 16" × 8" | 8" foundation wall | 0.33 |
| 20" × 10" | 10" wall / 2-story | 0.51 |
| 24" × 12" | Heavy / engineered | 0.74 |
Measure run length along the footing centerline so corners aren't double-counted. Trench pours into irregular soil often run 10–20% over the math — order accordingly.
Common questions
How much concrete do I need for footings?
Total footing length × width × depth (converted to feet) ÷ 27. A typical 50-foot run of 16" × 8" footing needs about 1.65 cubic yards — the calculator handles any run and section size, and footings are nearly always a ready-mix order, not bags.
How wide and deep should footings be?
The rule of thumb: footing width = 2× the wall thickness (so 16" under an 8" wall) and depth equal to the wall thickness, minimum 8". Soil bearing capacity and your local code make the final call — soft soils need wider footings.
How deep do footings need to be in the ground?
The bottom of the footing must sit below the frost line on undisturbed soil — anywhere from 12" in the South to 48"+ in northern states. This is the most commonly enforced inspection item in foundation work.
Do footings need rebar?
Standard practice (and most codes) call for at least two continuous runs of #4 rebar, lapped 20"+ at splices and corners, held 3" off the soil on chairs. Add vertical dowels if a poured or block wall goes on top.