Preparation
Self-levelling compound quantity and bags
- where
- volume to fill (litres)
- area to level (m²)
- average depth (mm)
- compound needed (kg)
- consumption per mm depth (kg/m² per mm)
- allowance for losses (%)
- bags to buy
- bag size (kg)
Explain this equation
Works out how much self-levelling compound to buy for a floor from its area and average depth.
A is the area and d the average depth in millimetres, so V = A × d gives the volume in litres. Cl is the product's consumption in kilograms per square metre per millimetre of depth. M is the powder needed with a loss allowance w, and B the bags of size Bs.
A square metre one millimetre deep holds exactly one litre, so area times depth is the volume in litres. Cl is the weight of powder per litre of laid compound, so multiplying the volume by Cl gives the kilograms of powder.
Sense check: at about 1.75 kg/m² per mm, a 20 kg bag covers about 3.8 m² at 3 mm, or about 2.3 m² at 5 mm.
Watch out: use the average depth from a grid of readings, not the deepest point. Respect the product's minimum and maximum thickness.
Powder needed to level a floor: area times average depth gives the volume, and the product’s consumption per millimetre converts it to kilograms and bags.
Enter your values to see the result.
Good to know
Consumption per mm in kg/m² is the same number as the laid density in kg/litre. BAL Level Plus covers about 3.8 m² per 20 kg bag at 3 mm with water (about 1.75 kg/m²/mm), 2–12 mm neat and up to 30 mm with aggregate. Find the average depth with a laser or straight-edge and a grid of readings; fall to a drain needs averaging over the fall. Prime first as the data sheet states.
Common mistake
Using the deepest point as the depth across the whole floor, which can double the order, or the shallowest, which leaves you short mid-pour.
Limits
Average-depth method only. Check the product’s minimum and maximum thickness and whether it needs aggregate or a fibre grade over timber.
Sources
Results are calculations from the published methods and manufacturer figures shown, and depend on the data you enter. Always follow the tile, adhesive and grout manufacturers’ instructions, BS 5385 and the Tile Association guidance. Coverage rates vary by product and substrate. Check prices and VAT rules with your own records and HMRC.