How much concrete do I need?

Enter your dimensions and the calculator multiplies length × width × thickness to give the volume, then converts it to cubic yards and the number of 40, 60 or 80 lb bags.

Should I order extra?

Yes — it's common to add about 5–10% for spillage and uneven subgrade so you don't run short mid-pour.

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Concrete Calculator

Estimate concrete for slabs and footings.

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How to use the Concrete Calculator

1Enter the length, width and thickness of your slab or footing.
2Choose your units (feet/inches or metric).
3Read the volume in cubic yards/metres and the number of bags needed.

About the Concrete Calculator

Free concrete calculator — work out how many cubic yards or bags of concrete you need for a slab, footing or column from your measurements. Instant results in imperial or metric.

Part of our Calculators collection. Browse all tools.

Frequently asked questions

How much concrete do I need?: Enter your dimensions and the calculator multiplies length × width × thickness to give the volume, then converts it to cubic yards and the number of 40, 60 or 80 lb bags.
Should I order extra?: Yes — it's common to add about 5–10% for spillage and uneven subgrade so you don't run short mid-pour.