Screed calculator
Enter the floor area in m² and the screed depth in mm to get the volume, the weight in tonnes and how much sand and cement a 4:1 mix needs.
Estimates only. Check the manufacturer's coverage rates.
How this is calculated
The volume is area x depth: volume (m³) = area (m²) x depth (mm) / 1000. An allowance is then added, 5% by default, for an uneven base and losses during mixing. A 20 m² floor at 50 mm is 1 m³, or 1.05 m³ with the allowance.
Weight assumes a screed density of 2,100 kg per m³, so tonnes = volume with allowance x 2.1.
The mix is 4 parts sand to 1 part cement by volume. Because sand and cement weigh different amounts, the calculator splits the weight using bulk densities of 1,600 kg per m³ for sand and 1,440 kg per m³ for cement. That makes cement (1 x 1,440) / (4 x 1,600 + 1 x 1,440), about 18.4% of the dry weight, with sand making up the rest. Cement tonnes are converted to 25kg bags and rounded up.
Water is not included, and the bulk densities are assumptions. Typical minimum depths are 25 mm for bonded screeds, 50 mm for unbonded screeds and 65 mm for floating screeds; check the specification for your floor.
- Typical minimum depths: bonded 25 mm, unbonded 50 mm, floating 65 mm. Check the specification for your floor.
- Assumed densities: screed 2,100 kg/m³, sand 1,600 kg/m³, cement 1,440 kg/m³. Water is not included.
Frequently asked questions
What is a 4:1 screed mix?
4 parts sand to 1 part cement by volume.
How much does screed weigh?
This calculator assumes 2,100 kg per m³, so 1 m³ is about 2.1 tonnes.
How thick should a screed be?
Typical minimum depths are 25 mm bonded, 50 mm unbonded and 65 mm floating. Check the specification for your floor.
Does the result include water?
No. It covers sand and cement only.