Cement, Sand & Aggregate Calculator
Split a concrete or mortar mix into bags of cement and volumes of sand and aggregate.
About the Cement, Sand & Aggregate Calculator
Nominal mixes give the proportion of cement : sand : aggregate by volume. Because dry materials shrink when water is added and voids fill, the dry volume is about 1.54 times the wet volume for concrete (1.33 for mortar). Cement's bulk density is taken as 1,440 kg/m³, so a 50 kg bag is about 0.0347 m³.
The formula
Cement (m³) = wet volume × 1.54 × cement parts ÷ total parts; bags = m³ × 1440 ÷ bag kg
Common nominal mixes
| Grade | Cement : sand : aggregate | Typical use |
|---|---|---|
| M10 | 1 : 3 : 6 | Levelling, blinding |
| M15 | 1 : 2 : 4 | Paths, plain concrete |
| M20 | 1 : 1.5 : 3 | Slabs, beams, columns (RCC) |
| M25 | 1 : 1 : 2 | Heavier structural work |
Worked example
Example: Cement = 7.3 bags
- Inputs: Wet volume: 1 m³; Mix: M20 concrete (1:1.5:3); Cement bag: 55 kg.
- Formula: Cement (m³) = wet volume × 1.54 × cement parts ÷ total parts; bags = m³ × 1440 ÷ bag kg
- Result: Cement = 7.3 bags
Things to keep in mind
- For structural concrete above M20, use a design mix by weight, not nominal volume proportions.
Questions people ask
Why multiply by 1.54?
Dry materials pack down by about a third when mixed with water.
How much water?
A water–cement ratio of about 0.45–0.55 by weight for most mixes.