About this calculator

This tool helps you estimate concrete for simple shapes before you order bags or speak with a supplier.

What goes into the estimate?

We calculate the volume of a rectangular slab, a solid round column, or a rectangular footing. You choose how much extra to allow for waste. Bag estimates use approximate manufacturer yields and are rounded up separately for each bag size.

What it cannot tell you

It cannot choose a safe foundation, slab thickness, reinforcement, concrete strength, or mix. It does not account for voids, steps, irregular excavations, or material displaced by a post. Building requirements depend on the site and project. Ask a qualified professional for design advice.

Check the method

See the FAQ for formulas, assumptions and manufacturer references. Confirm product yield and project requirements before ordering.