Floor Sanding Calculator — Belts, Discs & Lacquer

For standard renovation: start at 40 grit, then 60, 80 and finish at 120. For heavily damaged floors, start at 24 grit. For light refinishing, 80 and 120 grit may be sufficient. Never skip more than one grit level.

A drum sander belt typically covers 10–20m² of floor before needing replacement (a trade estimate — actual life depends on grit, timber hardness and old finish). For a 20m² room with 4 grit passes, this calculator's default model gives around 8 drum belts and about half as many edger discs (roughly 4), because the edges are only a small fraction of the floor area. There is no British Standard for abrasive consumption, so treat all belt and disc figures as estimates.

Apply 3 coats of water-based floor lacquer at approximately 0.1 L/m² per coat (a typical figure for products such as Bona Traffic HD and Manns Extra Tough). For a 20m² room, that’s 6 litres total. Sand lightly with 120 grit between coats. Hardwax oils are NOT the same rate: Osmo Polyx-Oil Original covers roughly 24 m²/L per coat (about 0.04 L/m²), less than half the lacquer rate, so do not use the lacquer figure for oil. Bona Traffic HD covers 8–10 m²/L per coat by roller — always check the product data sheet.

Gap filler (a resin such as Bona Mix & Fill or Lecol 7500, mixed with fine sanding dust) fills gaps between floorboards before final sanding. Manufacturers publish no fixed kg/m² rate because consumption depends entirely on gap width and board condition, so 0.05 kg/m² here is only a rough estimate for an average floor — allow more for wide gaps or a heavily gapped floor, and less for a tight floor.

A typical 15–20m² room takes 1–2 days for sanding (4 grit passes plus edging), plus drying time between lacquer coats (4–6 hours each). Allow 3–4 days total for the complete process.