Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate concrete volume for a continuous strip footing by its own width and depth in inches.
A footing is the buried, load-bearing base a foundation wall (or sometimes a fence or deck) sits on -- a long, continuous strip of concrete rather than a flat slab. Because a footing's cross-section is usually much narrower than a slab and specified by its own width and depth in inches, this calculator asks for those dimensions directly instead of the "thickness" language used by slab tools.
Enter the total run length of the footing in feet (for a foundation footing, this is usually the building's perimeter), then the footing's width and depth in inches -- both commonly specified by a structural plan or local building code, typically in the 12-24 inch range for residential work.
Volume (cu ft) = Length (ft) × Width (in ÷ 12) × Depth (in ÷ 12)
Both the width and depth get converted from inches to feet before multiplying, since the run length is already in feet. The result is the volume of one continuous strip -- if your foundation has, say, a long run plus a shorter perpendicular run, add both runs' lengths together first (or calculate them separately and sum the volumes).
This is the calculator to use before pouring the perimeter footing under a foundation wall, a shed, or a fence line that needs a continuous concrete base rather than individual post holes (for individual posts, see the Concrete Column Calculator or the Fence Post Calculator). Once you have a footing sized, the Concrete Wall Calculator sizes the foundation wall that typically gets poured on top of it.
Footing width and depth are structural decisions that depend on soil bearing capacity, wall load, and local frost-depth requirements -- they should come from an approved plan or your local building code, not guessed. This calculator only converts dimensions you already know into a concrete volume; it doesn't size the footing itself.
Consider a shed 20 ft by 15 ft with a continuous footing all round. The total run is 20 + 15 + 20 + 15 = 70 ft. If the plan calls for a footing 16 in wide and 8 in deep, the volume is 70 × 1.333 × 0.667, which is about 62.2 cubic feet. Adding a 10 percent allowance gives roughly 68.4 cubic feet, or about 2.53 cubic yards. Because footings are usually poured into trenches with uneven walls, the extra margin is worth keeping.
70 × (16 ÷ 12) × (8 ÷ 12) = 62.2 cu ft
The calculator assumes a clean rectangular section of constant width and depth. In practice trench sides can cave or be dug wider than the form, and the bottom is rarely perfectly flat. If you are pouring directly against soil rather than into forms, expect to use more than the theoretical figure. Check the trench for loose soil and standing water before the pour, and follow your inspector's schedule for when the excavation must be approved.
Dimensions, reinforcing steel, and depth below the frost line are engineering and code decisions. If you are unsure, ask your local building department what they require for your structure and soil. This calculator will then convert those approved dimensions into a volume you can order against.
It depends on the load above it and local soil conditions -- 16 inches is common for a typical residential foundation wall, but always follow your local building code or an engineer's spec rather than a rule of thumb.
The footing is the wide, shallow base poured first, directly on undisturbed soil, to spread the building's load. The foundation wall is poured on top of the cured footing and is typically narrower but taller -- see the Concrete Wall Calculator for that shape.
In cold climates, footings usually need to sit below the local frost line to prevent frost heave -- this affects the footing's depth below grade, which your local building code will specify. This calculator just needs the final depth number you're pouring.
Yes -- add up the total linear footage of every footing run (all four sides of a rectangular foundation, for example) and enter that as the length.
No. Reinforcing bars take up a negligible share of the volume and are not subtracted, so the estimate is safe for ordering.
Calculate each width and depth combination separately, then add the volumes together before deciding your order size.
Not automatically. The correct size depends on the load and the soil bearing capacity, so use the plan or code requirement rather than choosing a bigger size by feel.