Online Tool Store
Screed Calculator
Calculate floor screed volume in cubic meters plus the cement bags and bulk sand needed, from room dimensions, depth, and a 1:3 or 1:4 sand-cement mix ratio.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Total Screed Volume
Cement Bags Needed
Sharp Sand / Aggregate
How it works
- Enter the length and width of the room to calculate floor surface area.
- Specify the desired screed depth (e.g. 65mm for underfloor heating or 50mm for unbonded screeds).
- Select your mix ratio (1:4 traditional, 1:3 heavy duty, or ready-mixed bags) and cement bag weight.
- Review total screed volume in m³, cement bag counts, and bulk tonnes of sharp sand needed.
The formula
Screed Volume (m³) = Length (m) × Width (m) × Depth (m) × (1 + Waste %)
Total Screed Mass (kg) = Volume (m³) × 2,000 kg/m³
Cement Bags = ⌈(Total Mass / Total Mix Parts) / Bag Weight⌉
FAQ
What is the standard minimum depth for floor screed?
For bonded screed applied directly to a concrete base, the minimum depth is 25mm to 30mm. For unbonded screed over a damp-proof membrane (DPM), minimum thickness is 50mm. For floating screed over insulation or underfloor heating pipes, 65mm to 75mm is recommended.
What is the ideal sand-to-cement ratio for floor screeds?
A 1:4 mix (1 part Portland cement to 4 parts coarse sharp screeding sand) is the industry standard for domestic flooring. A richer 1:3 mix is used for heavy-duty commercial floors subjected to heavy rolling wheel loads.
How long does concrete floor screed take to dry before tiling?
Traditional sand-cement screed dries at a rate of approximately 1mm per day up to 50mm, and 0.5mm per day for depths beyond 50mm under standard ambient conditions (20°C and 50% relative humidity).
Why is a 10% waste allowance recommended?
A 10% allowance accounts for compaction during laying, irregular subfloor dips, and minor mixing spillage.
Can I enter room dimensions in feet instead of meters?
Yes - length and width can be entered in meters or feet, and depth in millimeters or inches, so you can work in whichever units your measurements are already in.
How we compare
| Feature | Online Tool Store | Merchant ready-reckoners | Manual estimation |
|---|---|---|---|
| Exact bulk bag (850kg) sand conversion | ✓ | ✗ | ✗ |
| Compaction and subfloor waste factor | ✓ | ✓ | ✗ |
| Support for ready-mixed screed bags | ✓ | Partial | ✗ |