How much paint do I need?
The basic formula is: litres = (width × height × coats) / coverage. Most interior emulsion paints quote 10–14 m² per litre per coat on a smooth previously-painted surface; on bare plaster or porous wood, coverage drops to 6–8 m²/L for the first coat.
Plan for two coats
Even with "one-coat" paint, two coats give a more even finish. For a colour change (e.g. light over dark), three coats may be needed. Always buy 10–15% extra to allow for touch-ups and slight under-estimation.
Quick reference
- 1 m² wall, 2 coats, 10 m²/L coverage → 0.2 L paint
- 10 m² wall, 2 coats → 2 L paint (a small tin)
- 50 m² wall, 2 coats → 10 L paint (a medium bucket)
FAQ
Should I subtract windows? Subtract them only if they are large; small windows are usually within the safety margin.
How does primer factor in? Primer is normally applied as one coat of a separate product, with similar coverage. Calculate it independently.