How to use the Concrete Calculator
Enter the length, width and thickness (or depth) of the element and choose the mix. The calculator uses the standard dry-volume factor of 1.54 and a 50 kg cement bag volume of 0.0347 m³ to estimate materials.
Nominal mixes: M10 = 1:3:6, M15 = 1:2:4, M20 = 1:1.5:3, M25 = 1:1:2. For structural work, design mixes and engineer approval are recommended.
Frequently asked questions
Why multiply by 1.54?
Dry materials shrink in volume when mixed with water and compacted. Multiplying wet volume by about 1.54 gives the dry volume of materials needed.
How many cement bags for 1 cubic metre of M20?
Roughly 8 bags using the nominal 1:1.5:3 mix and the dry volume method.