Subfloor & Floor Leveling Calculator
Calculate subfloor panels, floor leveling compound and acoustic underlay for floor preparation. Get quantities for OSB, tongue-and-groove chipboard, self-leveling compound and screed before any flooring installation.
How the floor preparation calculator works
- 1Panel count: floor area ÷ sheet area (e.g. 2400×600 mm = 1.44 m²), plus 5% waste
- 2Self-leveling compound: area × average depth (mm) × density (1.5 kg/L typically)
- 3Primer: area ÷ spreading rate (typically 5–8 m²/L for diluted PVA)
- 4Acoustic underlay: floor area + 10% for laps and cuts
- 5Screed thickness: minimum 50 mm over underfloor heating pipes, 65 mm without
- 6Round panels up to nearest sheet; compound up to nearest 25 kg bag
Worked example
Living room: 5 × 4 m = 20 m². Installing T&G chipboard panels (2400×600 mm). Average leveling depth 5 mm.
Panels: 20 ÷ 1.44 × 1.05 = 14.6 → 15 panels. Leveling compound: 20 m² × 5 mm = 100 L × 1.5 kg/L = 150 kg (6 bags of 25 kg).
Frequently asked questions
What thickness subfloor do I need?
18–22 mm T&G chipboard or OSB is standard for joisted floors with up to 450 mm joist spacing. Thicker boards (22 mm) are needed at wider joist spacings or for heavy loads. Concrete subfloors need only leveling compound.
When do I need self-leveling compound?
When the floor deviates by more than 3 mm over 2 m for thin flooring products (LVP, laminate) or more than 5 mm for thicker materials (tiles, solid wood). Pour compound over primed concrete and allow to cure fully before laying flooring.
How long does floor leveling compound take to dry?
Light foot traffic: 2–4 hours for most products. Flooring installation: 24 hours minimum for standard compounds, up to 7 days for deep pours (>10 mm). Check the product data sheet for your specific compound.
Do I need to prime before self-leveling compound?
Yes — always prime porous surfaces (concrete, screed, existing leveling compound) with diluted PVA or a specialist floor primer. This prevents the compound drying too fast, improves adhesion and prevents pinholing.
What is the difference between screed and self-leveling compound?
Screed is a sand-cement mix installed at 40–75 mm depth — it provides the structural layer over a concrete slab. Self-leveling compound is a thin-layer (3–10 mm) finishing product that flows level — used to achieve the final flatness tolerance for flooring.