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Paint Calculator (Litres)

Work out how many litres of paint a room needs, and which tins to buy. Every assumption is editable.

Room lengthRoom widthSeen from aboveDoorWindowWall heightOne wall
Key Where each paint measurement is taken.
Units
m
m
Typical ceiling. About 2.4 m in newer homes. Older homes are often higher. Editorial rule of thumb.
m
m²

If you fill this in, it is used instead of the room size for the walls.

Typical door. The most typical internal door in England and Wales is 1981 x 762 mm (6 ft 6 in x 2 ft 6 in), about 1.5 m². A 838 mm wide door is 1.66 m². Scotland often uses 2040 mm doors. Source: Howarth Timber, listed below.
m²
Windows vary a lot. The starting figure is only a placeholder. Measure each window you will not paint.
m²
m²/L

Check the tin. The starting figure is cautious.

%
£

Adds an estimated cost for the suggested sizes.

Paintable area33.1 m²
Paint needed, 2 coats5.52 L
Paint to buy, with waste6.1 litres
Suggested tins1 × 2.5 L + 4 × 1 L (6.5 L)

Walls: 2 × (4 + 3.5) × 2.4 m = 36 m², minus doors and windows 2.9 m², gives 33.1 m² to paint. × 2 coats = 66.2 m²; ÷ 12 m²/L = 5.52 L; with 10% waste = 6.07 L.

Porous, rough or dark surfaces need more paint. Check the coverage on the tin.

Fig. 1 Paint for your room.

Every formula is tested against worked examples. How we check

CoatsPaint to buySuggested tins
1 coat3.03 L1 × 2.5 L + 1 × 1 L
2 coats6.07 L1 × 2.5 L + 4 × 1 L
3 coats9.10 L1 × 5 L + 1 × 2.5 L + 2 × 1 L

Fig. 2 The same room at one, two and three coats.

Last checked 10/11/2026. Sources: Dulux UK: Dulux Matt (coverage up to 14 m² per litre); Dulux Trade Paint Expert: Vinyl Matt (up to 17 m² per litre); Howarth Timber: UK door sizes (1981 x 762 mm is the most typical internal size in England and Wales).

Guide

How the amount is worked out

Wall area = 2 × (length + width) × height. Take away the doors and windows, add the ceiling if you are painting it, multiply by the number of coats, then divide by how far a litre spreads. Finally add a little extra for waste.

Example. A 4 × 3.5 m room with 2.4 m walls has 36 m² of wall. One door (1.9 m²) and one window (1.4 m²) leave 32.7 m². Two coats make 65.4 m², and at 12 m² per litre that is 5.45 litres before waste, about 6 litres with 10% extra.

Where the 12 m² per litre comes from

Dulux lists coverage of up to 14 m² per litre for its Matt emulsion and up to 17 m² per litre for Dulux Trade Vinyl Matt, and "up to" figures are best-case. The tool starts lower, at 12, so that you are less likely to run short. Rough plaster, new plasterboard, dark colours and strong colour changes all need more, so check the coverage on your tin.

Common mistakes

  • Forgetting the second coat. Most rooms need two.
  • Buying exactly the figure shown. Keep a little for touch-ups.
  • Treating the door and window sizes as exact. They are averages; measure large windows and patio doors and use the direct wall-area box.
  • Skipping primer or mist coat on new plaster. That is a separate product with its own coverage on the tin.

Pack sizes

The suggested tins use 1 litre, 2.5 litre, 5 litre and 10 litre sizes. The tool picks the least paint that covers the amount using the fewest tins. Sizes vary by brand, so treat it as a starting point.

Common questions

How many litres of paint for a 4 x 3.5 m bedroom?

With 2.4 m walls, one door, one window and two coats, a 4 x 3.5 m room needs about 5.5 litres, or about 6 litres with 10% for waste, at 12 m² per litre. Try it in the calculator above.

Do I paint the door and window area?

No. The calculator subtracts them. If your windows are large or you have lots of woodwork, change the deduction.

Does the ceiling use the same paint as the walls?

Often not; ceilings usually take a ceiling paint. Run the tool once for the walls and once for the ceiling if you want separate quantities.

Does the skirting board count?

Not here. Woodwork usually takes a different paint, so work it out separately with its own coverage.

Worked examples

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