Concrete Footing Calculator
Calculate cubic yards of concrete for a strip footing from its length, width, and depth, plus total cost at your price per yard.
How this calculator works
A continuous strip footing is a long, narrow concrete form, so this calculator treats it as a simple rectangular volume: the total footing run (length), the footing’s width, and the footing’s depth. Footing sizing itself is a structural decision — this tool only converts your specified dimensions into cubic yards and cost.
Formula: Cubic yards = (Length ft × Width ft × Depth ft) ÷ 27.
Worked example
A 20 ft footing run, 2 ft wide, at a 12-inch depth, $150/yd³:
- Depth in feet: 12 ÷ 12 = 1.000 ft
- Cubic yards: (20 × 2 × 1.000) ÷ 27 ≈ 1.48 yd³
- At $150/yd³, that’s $222.22 before waste.
Coverage reference
| Footing run | Width | Depth | Concrete needed |
|---|---|---|---|
| 20 ft | 2 ft | 12 in | 1.48 yd³ |
| 40 ft | 2 ft | 12 in | 2.96 yd³ |
| 60 ft | 2 ft | 18 in | 6.67 yd³ |
How to measure your footing
Walk the planned footing line and total up every straight run in feet — for a rectangular foundation, that’s the perimeter. Width and depth come from your foundation plan, not a guess; footing sizes are structural and must match your local building code or an engineer’s specification for the soil conditions and loads involved. This calculator only converts confirmed dimensions into concrete volume, it doesn’t determine what those dimensions should be.
Frequently asked questions
What do the length, width, and depth fields mean for a footing?
Length is the total run of footing (add up every straight section if it's not one continuous line), width is the footing's width, and depth is the footing's depth — not the depth of any wall or slab it supports.
How do I know what size my footing needs to be?
Footing width and depth are structural decisions based on soil bearing capacity, frost depth, and the load the footing carries — they are not something to estimate. Always confirm dimensions against your local building code or a structural engineer's specification before ordering concrete.
Why does footing depth usually relate to frost line?
In climates with freezing winters, footings are typically required to sit below the local frost depth so seasonal freeze-thaw cycles don't heave the foundation. Frost depth requirements vary widely by region, so check your local code rather than assuming a standard number.
Should I add extra concrete for waste on a footing pour?
Yes — trench excavation is rarely perfectly uniform, so 10% is a reasonable buffer for over-dig and minor spillage. Running short mid-pour on a footing is a bigger problem than a small leftover amount.
Do I need rebar in a concrete footing?
Most residential footings call for continuous rebar for tensile strength, with the size and placement specified by code or an engineer based on the load and soil conditions. This calculator estimates concrete volume only — rebar is a separate material and labor item.
Estimates only. Verify quantities with your supplier before purchasing.