Self-Levelling Compound Calculator — How Many Bags Do I Need?

At a typical 3mm depth, one 25kg bag of standard self-levelling floor compound covers approximately 5–5.5 m². At 2mm depth, coverage increases to around 7–8 m² per bag. Coverage varies by brand — always check the manufacturer’s data sheet. Popular UK brands include Setcrete, Mapei, Weber and Ardex. For deeper levelling or full screed work, use our Screed Calculator.

Standard self-levelling compound is typically applied at 2–5mm thickness. For deeper fills (5–50mm), you need a deep-fill or thick-bed self-levelling product such as Setcrete Deep Flow or Weber Floor 4160 — our Floor Levelling Calculator covers deep-fill products too. Never exceed the manufacturer’s maximum thickness in a single pour as this can cause cracking.

Yes, always prime the floor before applying self-levelling compound (also called floor leveller or floor smoothing compound). The primer seals the substrate, prevents air bubbles, and improves adhesion. Primer coverage depends heavily on subfloor absorbency and dilution: on an absorbent concrete or screed subfloor, diluted acrylic primer covers up to around 20 m² per litre (Setcrete Acrylic Primer covers ~50 m² from a 2.5 litre bottle diluted), while neat primer on a non-absorbent surface covers closer to 10 m² per litre. Our calculator defaults to a conservative 1 litre per 5 m² so you don’t run short — adjust this in the advanced options to match your product’s data sheet. Most manufacturers produce a matching primer, and using the same brand is recommended.

Standard self-levelling compound is typically walkable after 2–4 hours and ready for tiling after 12–24 hours. Fast-set compounds can be tiled over in as little as 45 minutes to 2 hours. Once ready, use our Floor Tile Calculator to work out how many tiles, adhesive and grout you need. Always check the product data sheet, as humidity and temperature affect curing times.

Yes, but the wooden floor must be structurally sound and rigid — check the joist spacing and condition with our Floor Joist Calculator. Use a flexible, fibre-reinforced self-levelling compound designed for use over timber substrates. You may also need to apply a decoupling membrane or use screws to secure any loose boards. Standard rigid compounds may crack on timber floors due to movement.