Free Paint Calculator
Work out how many litres of paint you need for a room: walls, openings, coats and optional ceiling.
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.
Results
Fill in the details and select Calculate to see your figures.
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Get a free demoHow to use the Paint Calculator
- 1Choose room length + width, or enter the full wall perimeter if you already measured it.
- 2Set wall height (UK rooms are often 2.4m).
- 3Enter doors and windows so their area is subtracted.
- 4Set coats (usually 2) and coverage if you are not using standard emulsion.
- 5Toggle ceiling on if you are painting that too: it uses room L × W.
How to work it out yourself
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 |
Disclaimer
This tool gives an estimate for general guidance only, based on typical UK figures and the details you enter. It is not a formal quote, survey, or professional advice. Always confirm with a qualified tradesperson before relying on any figure, as regional prices, site conditions, and current standards vary.
You do the job, Tradehand handles everything around it.
Tradehand sends the quotes, chases the invoices, books the work and keeps your customers updated, for no monthly fee and 5% of an invoice only once the customer has paid. One office hire costs about £25,000 a year, whether the invoices land or not.
Source: Office manager salary, National Careers Service
Get a free demoFrequently 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.
