Concrete Calculator

Enter the slab length, width, thickness and wastage percentage to estimate the volume of concrete.

This result is an estimate only. Check with your bank or the relevant authority before making decisions.

How it is calculated

Volume (m³) = length × width × thickness (m) × (1 + wastage)
Thickness in metres = millimetres ÷ 1000
Cubic feet = m³ × 35.3147

This estimate is for a rectangular slab.

Worked example

A 4 m × 3 m slab, 100 mm thick, 5% wastage:

4 × 3 × 0.1 × 1.05 = 1.26 m³
1.26 × 35.3147 = 44.5 ft³

Why your number may differ

Uneven ground, spillage and a slab that is not a plain rectangle can change the real quantity. Order ready-mixed concrete by the cubic metre, and confirm the amount with your supplier.

Frequently asked questions

How is concrete volume calculated?

Multiply length, width and thickness (in metres), then add the wastage percentage.

How is ready-mixed concrete ordered?

Ready-mixed concrete is ordered by the cubic metre. Confirm the amount with your supplier.

How many cubic feet are in a cubic metre?

One cubic metre is about 35.3147 cubic feet.