Calculate your concrete
Select the shape and unit, then enter the required dimensions. Only the dimensions for your selected shape are used.
How the calculation works
- Measure the shape. Use the same selected unit for all dimensions.
- Calculate its volume. Multiply length by width by depth for a rectangular shape. For a cylinder, use pi times radius squared times height.
- Add waste. The calculator increases the base volume by the waste percentage you enter.
- Estimate bags. The waste-adjusted volume is divided by the yield per bag, then rounded up to a whole bag.
Conversion reference
| Unit | Equivalent |
|---|---|
| 1 cubic metre | 1.30795 cubic yards |
| 1 cubic metre | 35.3147 cubic feet |
| 1 cubic metre | 1,000 litres |
Frequently asked questions
How much concrete does a 5 m by 3 m slab need?
At a thickness of 0.15 m, the volume is 5 × 3 × 0.15 = 2.25 m³ before waste. With a 10% allowance, the estimated order volume is 2.475 m³.
How are concrete bags calculated?
The calculator divides the waste-adjusted cubic metres by the yield per bag you specify, then rounds up. Always use the yield stated on the product packaging.
Can I calculate a circular column?
Yes. Select Cylinder / circular column and enter the diameter and height. The calculator converts the dimensions into metres before calculating the cylinder volume.
Should I add a waste allowance?
A waste allowance may help account for uneven surfaces, minor spills and measurement variation. The appropriate amount depends on your project and site conditions.