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Floor Levelling Calculator — Compound & Materials Estimator
Estimate how much levelling compound you need to level an uneven floor. Covers self-levelling, floor patch and deep fill products.
Total floor area of the room
Measure at multiple points and take the average
Adds 10% extra for uneven areas and mixing losses
10% recommended for most levelling work
Enter your supplier price for a cost estimate
Weight per bag of compound (default 25kg)
Area covered per litre, neat (default 10 m²/L). Acrylic primers cover ~8–12 m²/L neat (Sika Level-01) up to ~25 m²/L (Setcrete); diluting on porous screed can reach ~50 m²/L — check your primer's data sheet
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How We Calculate This
Our floor levelling calculator estimates the amount of compound needed based on your floor area and the average depth of unevenness. Different products have different coverage rates and are designed for different depth ranges.
The formula
Bags needed = (Area × Average depth × Coverage rate) ÷ Bag size
For example, levelling 15 m² at an average 3mm depth with self-levelling compound (1.6 kg/m²/mm): 15 × 3 × 1.6 = 72 kg ÷ 25 = 3 bags (before wastage).
Coverage rates by product type
- Self-levelling compound: 1.6 kg/m²/mm — best for 2–5mm depth, flows to a level finish (e.g. Mapei Ultraplan; Weber and Setcrete High Performance run a little higher at ~1.7)
- Floor patch/repair: 1.5 kg/m²/mm — for localised dips and feathered repairs, 1–10mm (e.g. Mapei Planipatch; Planipatch Xtra 1.4)
- Deep fill compound: 1.9 kg/m²/mm — for 5–50mm depth, often used before self-levelling (e.g. Setcrete Deep Base ≈1.86 kg/m²/mm at 5mm rising to ~2.0 at 20–50mm)
These rates are based on typical UK products from Setcrete, Mapei, Weber and Ardex ranges. Deep-fill compounds are the heaviest per millimetre and patch/feather compounds the lightest, so always pick the product type that matches your depth and check the manufacturer's data sheet for the exact coverage rate. Primer is estimated at around 10 m² per litre (typical neat acrylic floor primer); diluting on porous screed can stretch this much further, so follow your primer's instructions.
Frequently Asked Questions
Use a long straight edge (spirit level or straight timber) across the floor. Measure the gap between the floor and the straight edge at multiple points. Take 5-10 measurements across the floor and calculate the average. For a floor that dips in the middle by 5mm but is level at the edges, the average depth might be 2-3mm. This floor levelling compound calculator uses the average depth to estimate material quantities.
For depths of 2–5mm, use standard self-levelling compound — try our Self-Levelling Compound Calculator for precise bag counts. For localised repairs of 1–10mm, use a floor patch/repair compound. For depths over 5mm (up to 50mm), use a deep-fill levelling compound. For full-depth screeding (50mm+), see our Screed Calculator. Never exceed the manufacturer’s maximum application depth in a single pour.
Yes, but you must use a flexible, fibre-reinforced compound designed for timber substrates. Standard rigid compound may crack on wooden floors due to movement. Check the structural integrity of your floor joists first with our Floor Joist Calculator. Secure any loose boards, apply a suitable primer, and consider using a decoupling membrane. Popular UK products for timber floors include Setcrete High Performance and Mapei Ultraplan Renovation.
Yes, always prime the floor before applying levelling compound (floor leveller or floor smoothing compound). The primer seals the substrate, prevents air bubbles rising through the compound, and improves adhesion. A typical neat acrylic floor primer covers around 8-12 m² per litre (e.g. Sika Level-01), and up to roughly 25 m² per litre for some brands (e.g. Setcrete); on porous screed the primer is usually diluted, which can extend coverage to around 50 m² per litre. Different substrates may need different primers and dilution ratios — check the compound manufacturer's recommendations.
Once the levelling compound has cured, you can lay any floor covering. Use our Floor Tile Calculator for tiles, Laminate Flooring Calculator for laminate, Vinyl Flooring Calculator for vinyl or LVT, or Carpet Calculator for carpet. Standard self-levelling compound is walkable after 2–4 hours and ready for floor coverings after 12–24 hours.
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.