Concrete Calculator

Calculate the concrete needed for slabs, footings and post holes in cubic metres, yards and bags.

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Results are estimates. Allow for waste, local conditions and supplier guidance before you buy.

About the Concrete Calculator

Get the volume of concrete for a rectangular slab or footing, or round columns and post holes, plus how many premix bags that is.

slab volume = length × width × depth
column volume = π × (diameter ÷ 2)² × height

How much does a bag of concrete make?

A 20 kg bag of premix makes roughly 0.0095 m³; an 80 lb bag about 0.6 cubic feet. Check the bag.