Free Paint Calculator
Work out how many litres of paint you need for a room: walls, openings, coats and optional ceiling. Free for UK decorators, no sign-up, answer in seconds.
Paint Calculator results
Fill in the details and select Calculate to see your figures.
This paint calculator works out paintable area and litres needed from room size or total wall length, height, coats and openings. It uses typical UK emulsion coverage of about 12 m² per litre per coat; adjust coverage for primer, gloss or porous surfaces.
How to use the Paint Calculator
- Choose room length + width, or enter the full wall perimeter if you already measured it.
- Set wall height (UK rooms are often 2.4m).
- Enter doors and windows so their area is subtracted.
- Set coats (usually 2) and coverage if you are not using standard emulsion.
- Toggle ceiling on if you are painting that too: it uses room L × W.
How the Paint Calculator works
Paint quantity follows the wall area: work it out, take off openings, multiply by coats, then divide by the coverage on the tin.
- Room 4m × 3.5m → perimeter 15m × 2.4m height = 36 m² walls.
- 1 door (1.8) + 1 window (1.6) = 3.4 m² openings → 32.6 m² paintable.
- 2 coats ÷ 12 m²/L → 32.6 × 2 ÷ 12 = 5.43 → buy 6 litres.
- Typical tin sizes are 2.5L and 5L: e.g. one 5L + one 2.5L, or two 5L for spare.
Coverage varies by surface and porosity. New plaster needs a diluted mist coat first. Always check the manufacturer's figure on the tin.
Typical UK benchmarks
- Emulsion coverage
- ~12 m²/L per coat (typical UK emulsion)
- Gloss / satinwood
- ~16 m²/L per coat
- Primer / mist coat
- ~10 m²/L; new plaster needs a mist coat first
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Frequently asked questions
How much paint do I need for a bedroom?
A typical 3.5m × 3m bedroom at 2.4m with one door and one window needs about 5–6 litres of emulsion for two coats. Always round up a tin so you can touch in later from the same batch.
How many m² does a litre of emulsion cover?
Most UK emulsions quote about 12 m² per litre per coat on a smooth, sealed surface. Rough, porous or dark-to-light colour changes need more: often closer to 8–10 m²/L.
Do I subtract doors and windows?
Yes for a realistic wall estimate. A standard door is about 1.8 m² and a typical window about 1.6 m². Large patio doors or bay windows should be measured and deducted properly.
How many coats of paint do I need?
Two coats of emulsion is standard over a similar colour. New plaster usually needs a mist coat then two full coats. Strong colour changes may need a primer or a third coat.
Should I paint the ceiling with the same calculation?
Ceiling area is simply room length × width: no door/window deduction. Use a ceiling white or matt emulsion; coverage is similar to walls if the surface is sound.
