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.

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.

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.

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Paint Calculator results

Fill in the details and select Calculate to see your figures.

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How 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 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.

paintable m² = (perimeter × height − openings) [+ ceiling] → litres = ceil(paintable × coats ÷ coverage)

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.

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Your assistant sends the quotes, chases the invoices, books the work and keeps your customers updated. The first £10,000 Tradehand collects for a business carries no Tradehand fee. After that, Tradehand earns 5% of collected invoice payments. No monthly fee, setup fee, card fee or contract. One office hire costs about £25,000 a year, whether the invoices land or not.

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