Self-Levelling Compound Calculator — How Many Bags Do I Need?
Calculate how many bags of self-levelling compound you need for your floor area. Covers standard, fibre-reinforced and fast-set products.
Typical 2-5mm for standard, up to 50mm for deep fill
Adds 10% extra for uneven areas and mixing losses
10% recommended for most levelling work
Enter your supplier price for a cost estimate
How We Calculate This
Our self-levelling compound calculator works by multiplying your floor area by the application depth and the compound's coverage rate (kg per m² per mm). We then divide by 25kg to give you the number of standard bags needed.
The formula
Bags needed = (Area × Depth × Coverage rate) ÷ 25kg
For example, a 20 m² floor at 3mm depth using standard compound (1.6 kg/m²/mm): 20 × 3 × 1.6 = 96 kg ÷ 25 = 4 bags (before wastage).
Coverage rates we use
- Standard compound: 1.6 kg per m² per mm — a 25kg bag covers ~5.2 m² at 3mm
- Fibre-reinforced: 1.7 kg per m² per mm — a 25kg bag covers ~4.9 m² at 3mm
- Fast-set: 1.5 kg per m² per mm — a 25kg bag covers ~5.5 m² at 3mm
Primer calculation
Primer is calculated at 1 litre per 5 m² of floor area, which is a standard coverage rate for acrylic floor primers. Rates are based on typical UK products from Setcrete, Weber, Mapei and Ardex ranges available at Screwfix, Toolstation and builders merchants.
Frequently Asked Questions
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Last updated: February 2026
All calculations are estimates. Verify with your supplier.