Floor Screed Calculator
Enter the room area and screed thickness to get the dry mix weight and the number of bags.
The formula
Kilograms = area × thickness (mm) × consumption. Bagged screed mixes use 1.8–2.0 kg/m² per millimetre. A traditional sand-cement screed needs roughly 300–330 kg of cement and 1.1–1.2 m³ of sand per cubic metre of mortar.
Worked example
A 20 m² room with a 50 mm screed at 2.0 kg: 20 × 50 × 2.0 = 2000 kg — eighty 25 kg bags. That is 2 m³ of material to carry and store, so ready-mixed delivery is often cheaper.
Minimum thickness
| Type | Minimum | Note |
|---|---|---|
| Cement screed on a slab | 30 mm | Thinner layers crack |
| Reinforced with mesh | 40–50 mm | Mesh sits mid-layer |
| Over underfloor heating | 30 mm above the pipe | Otherwise heat shows as stripes |
| Self-levelling compound | from 2–3 mm | Levelling only |
Weight and level differences
A 50 mm screed weighs about 100 kg per square metre. On a timber floor or an old slab that can be too much, and the limit is a structural question, not a calculator one. If the level varies by more than 5 cm across the room, levelling the base with expanded clay or a dry fill is cheaper than pouring mortar everywhere.
Construction Material Calculators
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