Self-Levelling Compound Calculator
Estimate how much self-levelling floor compound to buy, using your floor area, the average depth you need to fill and the coverage rate from the product's technical data sheet.
Results
Enter your project measurements to see your results.
What this calculator does
Self-levelling compound is sold by weight but used by thickness, so the link between the two is the coverage rate printed on the product: how many kilograms cover one square metre at one millimetre deep. The calculator multiplies your area by your average depth and that rate, adds your waste allowance once, and rounds the bag count up.
Measuring the floor
- Measure the length and width of the room at floor level, wall to wall.
- For L-shaped or irregular rooms, split the floor into rectangles, add their areas and use the total floor area option.
- Leave out fixed units or hearths that will not be covered.
Estimating average depth on an uneven floor
A floor that needs levelling is rarely the same depth everywhere. Set a straightedge or laser to the finished level and measure the gap at a grid of points, including the hollows and the high spots. The average of those readings is the figure to enter. The nominal depth you aim for, the average across the floor and the minimum or maximum thickness the product allows are three different things — the last is set by the manufacturer, not by this page.
Why coverage rates vary
Products differ in formulation, filler and density, and some are designed for thin smoothing while others build thicker layers. That is why the calculator asks for the manufacturer-stated rate rather than assuming one.
Worked metric example
A 4 m × 3 m kitchen is 12 m². At an average 5 mm with a stated rate of 1.6 kg/m²/mm, that is 12 × 5 × 1.6 = 96 kg. Adding 5% waste gives 100.8 kg, or 4.03 bags of 25 kg, so you would buy 5. The 1.6 figure is for illustration only.
Worked imperial example
A 12 ft × 10 ft room is 120 sq ft (11.15 m²). An average depth of 1/4 in is 6.35 mm. With a stated rate of 1.6 kg/m²/mm that is about 113 kg (250 lb) before waste — five 50 lb bags.
Self-levelling compound versus floor screed
Self-levelling compounds flow into place and are mostly used in thinner layers to give a smooth base for floor coverings. Traditional sand and cement screeds are laid thicker and compacted. For screed quantities, see the floor screed calculator; for concrete, the concrete slab calculator.
Preparation and suitability
Substrate preparation, priming, permitted thickness, underfloor heating and the right product for timber or other substrates all depend on the manufacturer's instructions. This calculator estimates materials only; it does not confirm that a product or thickness is suitable for your floor, structural or specialist work.
Frequently asked questions
- How much self-levelling compound do I need per square metre?
- Multiply the area by the average depth in millimetres and by the coverage rate on the product's technical data sheet, usually given in kg per m² per mm. For example, 1 m² at 3 mm with a stated rate of 1.6 kg/m²/mm needs 4.8 kg before waste.
- Why doesn't the calculator fill in a coverage rate?
- Coverage rates differ between products, so there is no universal figure. Find the rate on the bag or technical data sheet of the compound you are buying and enter that.
- How do I work out average depth on an uneven floor?
- Use a straightedge or laser level and measure the gap to the target level at several points across the floor, including the high and low spots. Add the readings together and divide by the number of readings.
- What thickness of self-levelling compound can I apply?
- Each product has its own minimum and maximum thickness, and these can vary with the substrate and whether the product is reinforced or layered. Check the manufacturer's data sheet. This calculator does not recommend a thickness.
- Is self-levelling compound the same as floor screed?
- No. Self-levelling compounds are flowable and usually applied in thin layers to smooth a floor before a floor covering. Traditional sand and cement screeds are laid much thicker and compacted by hand. They are different products with different uses.