About this calculator
Self-levelling compound for thin pours, or traditional sand:cement screed for thicker beds.
How it’s calculated
Volume = area × average depth. Self-leveller is taken at about 1.7 kg per m² per mm, so a 20 kg bag covers about 4 m² at 3 mm. Screed uses a dry-volume factor of 1.33.
Worked example
With these inputs:
- Measure by
- Length × width
- Length
- 4.5 m
- Width
- 3.6 m
- Average depth
- 5 mm
- Material
- Self-levelling compound (20 kg)
- Waste allowance
- 10%
the result is:
- Bags needed
- 8 bags
- Volume
- 0.09 m³
- Area
- 16.2 m²
Tips from the trade
- Measure depth on a grid with a straightedge and average it. Don’t guess.
- Prime the substrate, and seal gaps and drains so the leveller doesn’t run away.
- Thick pours may need a deep-fill product or aggregate added.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.