Material estimator

Concrete Footing Calculator

Estimate concrete for strip footings, continuous footings, and rectangular foundation pads.

How This Calculator Works

Footings often need a more conservative estimate than surface slabs because excavation and soil conditions are less predictable. This calculator estimates rectangular footing volume and bag counts.

Formula

Footing volume = length x width x depth x quantity. Width and depth are entered in inches and converted to feet.

Assumptions

This tool estimates material quantity only. Footing width, depth, reinforcement, and frost depth are design/code questions that must be confirmed separately.

Example

A 20 ft strip footing that is 16 inches wide and 12 inches deep needs about 26.7 ft^3 before waste, or 0.99 yd^3. With 10% overage, plan around 1.09 yd^3.

Before You Buy

This estimates volume after the footing size is already known; it does not size the footing structurally.
Below-grade forms and trench walls are rarely exact, so a conservative overage is more important than on a clean surface slab.
Keep rebar, chairs, form boards, vapor barrier, gravel, and inspection requirements separate from the concrete quantity.

Common Questions

Does this size the footing structurally?

No. It estimates material volume after you already know the required footing dimensions.

Why add overage below grade?

Excavated trenches are rarely perfectly rectangular, so overage reduces the chance of running short.

Can I use this for round piers?

Use the post-hole calculator for round holes and piers. This page is for rectangular strip or pad footings.