← All Calculators
Cement Calculator
Estimate cement bags for your project
Advertisement
Result
Ready to calculate...
What this calculator does
Estimates 50 kg bags of cement for a slab-shaped volume using a fixed 320 kg of cement per cubic meter.
How to use it
- Enter width, length and depth of the pour.
- Set the waste margin.
- Read the number of bags and the matching concrete volume.
Formula
baseVolume = Width × Length × Depth Cement Bags = roundUp( baseVolume × 320 / 50 × (1 + Waste Margin (%) / 100) ) Material volume m³ = baseVolume × (1 + Waste Margin (%) / 100)
Formulas are shown in metric units, exactly as the calculator computes them. Imperial entries are converted to metric first. Waste is applied as a multiplier (1 + waste/100).
Areas are in m² and volumes in m³. RoundUp means the next whole piece or bag.
Variables
| Variable | Unit | Default |
|---|---|---|
| Width | m | 4 |
| Length | m | 5 |
| Depth | m | 0.15 |
| Waste Margin (%) | % | 10 |
Worked example
Using the default values of this calculator (Width = 4 m, Length = 5 m, Depth = 0.15 m, Waste Margin (%) = 10 %), the calculator returns:
baseVolume = 4 × 5 × 0.15 Cement Bags = roundUp( baseVolume × 320 / 50 × (1 + 10 / 100) ) Material volume m³ = baseVolume × (1 + 10 / 100)
- Cement Bags: 22 bags (50kg)
- Concrete Volume: 3.3 m³
Assumptions and limitations
- The 320 kg/m³ figure is a fixed planning assumption (roughly a 1:2:4 mix), not a strength specification.
- The mix proportions are not editable; other mixes need different cement contents.
Waste, rounding and buying
Bags are whole units, so the result is rounded up. Buy a spare bag; cement hardens with moisture, so store it dry.
Frequently asked questions
- Can I change the cement content per cubic meter?
- No, 320 kg/m³ is fixed. If your mix specifies another content, scale the bag count proportionally.
- Does this give the sand and gravel?
- Not directly. Use the Sand and Gravel calculators for volumes, bearing in mind they use their own density assumptions.