What is the Concrete Calculator?
The concrete calculator finds the volume of concrete you need for a slab, path or footing, with a 10% allowance for waste and uneven ground.
How to use the Concrete tool
- Enter Length, Width and Thickness.
- The result updates instantly as you type, or press Calculate.
- Use Try an example to see how it works, and Reset to start again.
Formula
Volume = length × width × thickness. The tool adds 10% waste. One cubic metre is 1.30795 cubic yards.
Worked example
With length 4 m, width 3 m, thickness 10 cm, the concrete needed comes to 1.32 m³. Exact volume: 1.2 m³; In cubic yards (with 10% waste): 1.73 yd³.
Frequently asked questions
How thick should a slab be?
Residential slabs and paths are usually 10 cm, driveways 12 to 15 cm.
Why add waste?
Spillage, uneven subgrade and over-excavation all use extra concrete.
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Checked by Calcovate · Formula tested against worked examples · Updated 7 Nov 2026 · How we check our calculators.