How to use it
- Measure every run of footing and add them for the total length.
- Enter the footing width and depth from your plans.
- Keep 10% extra for trench walls that are wider than planned.
The formula
Volume = total length × width × depth
Cubic yards = cubic feet ÷ 27
Worked example
| Total footing length | 40 ft |
| Footing width | 16 in |
| Footing depth | 8 in |
| Waste / spillage allowance | 10 % |
Result
| Concrete needed | 1.45 cubic yards |
| Cubic feet | 39.1 ft³ |
| Cubic meters | 1.11 m³ |
| 80 lb bags | 66 bags |
| 60 lb bags | 87 bags |
| Approx. weight | 2.9 tons |
Tips before you order
- Trenched footings often end up wider than drawn; measure the actual trench before ordering.
- Footing depth and width are set by your local code and soil — the bottom must sit below the frost line in cold climates.
Questions
What size are typical house footings?
Under the IRC, many one- and two-story homes use footings 12–24 in wide and at least 6 in thick, but the required size depends on soil bearing capacity and the load — check your local code.