Ballast Calculator
Work out the ballast and cement needed to mix your own concrete.
Ballast required
2.1tonnes
- Cement
- 17 × 25 kg bags
- Concrete volume
- 1.2 m³
Based on a 1:2:4 concrete mix, about 1.75 tonnes of ballast and 350 kg of cement per cubic metre.
v1.0 · Reviewed September 2026
How this is worked out
The finished concrete volume is length × width × depth. Materials are then taken from a 1:2:4 mix, using 1.75 tonnes of ballast and 350 kg of cement for each cubic metre of finished concrete. Cement is rounded up to whole 25 kg bags.
Worked example
- Length 4 m
- Width 3 m
- Depth 100 mm
1.2 m³ × 1.75 = 2.1 tonnes ballast; 1.2 × 350 = 420 kg cement, so 17 bags
2.1 tonnes of ballast and 17 × 25 kg bags of cement
Assumptions and limits
- Quantities are for a 1:2:4 general purpose mix by volume. A different mix changes both figures.
- Water, plasticiser and reinforcement are not included.