Concrete Footing Calculator

A concrete footing calculator sizes the strip of concrete that spreads a wall or post load into the ground. Enter the total run of footing, its width and its depth, and it returns the volume of ready-mix in cubic yards or metres plus a bag count for shorter runs — all with 10% waste added.

Your measurements

Result

Footings are usually specified by an engineer or your local code: a typical residential strip footing is 16–24 inches wide and 8–12 inches deep. Measure the total length of every footing run and add them together for the figure to enter here.

How it is calculated

Footing volume is total length × width × depth, with width and depth converted from inches to feet. Because trenches are dug slightly oversize and bottoms are uneven, the 10% waste allowance matters more here than on a formed slab.

Steps

Add up the total length of all footing runs, in feet.
Enter the footing width in inches (16 inches is a common residential size).
Enter the depth in inches — usually 8–12 inches.
Read the cubic-yard total; this is almost always a ready-mix order, not bags.
Order with the 10% waste line, since trench bottoms are rarely perfectly even.

Worked example

A 40 ft footing run that is 16 inches wide and 8 inches deep is 40 ft × 1.33 ft × 0.67 ft = about 35.6 cubic feet, or 1.32 cubic yards — round up to roughly 1.45 yards with waste.

Common questions

How wide and deep should a footing be?

That is set by the load and soil, via your engineer or building code. As a rough guide, residential strip footings run 16–24 inches wide and 8–12 inches deep.

Do footings need rebar?

Most do — typically two or more continuous rebar runs near the bottom. Reinforcement is specified by the design; this tool sizes the concrete volume.

Can I pour footings with bags?

Only for very short runs. A normal house footing is several cubic yards, which is far cheaper and faster as a ready-mix delivery.

Should I pour footings and slab together?

Sometimes — a "monolithic" or thickened-edge slab combines them. For that, size the footing thickening and the slab separately and add them.