How to work out how much paint you need
Litres = area × coats ÷ coverage per litre
A standard internal door is about 1.6 m² and an average window about 1.5 m². Two coats are normal for a colour change; one coat may do when refreshing the same colour.
Paint for common rooms (walls, 2 coats, 12 m² per litre)
| Room | Size, 2.4 m walls | Paint |
|---|---|---|
| Small bedroom | 3.0 × 2.5 m, 1 door, 1 window | about 3.9 litres |
| Double bedroom | 4.0 × 3.5 m, 1 door, 1 window | about 5.5 litres |
| Living room | 5.0 × 4.0 m, 1 door, 2 windows | about 6.4 litres |
Worked example
A 4 m × 3.5 m bedroom with 2.4 m walls has 36 m² of wall, minus a door (1.6 m²) and a window (1.5 m²): 32.9 m². Two coats at 12 m² per litre need 5.5 litres, so buy 3 tins of 2.5 litres, or one 5 litre tin and a 2.5 litre tin.
Frequently asked questions
How much paint do I need for a bedroom?
For a 4 m by 3.5 m room with 2.4 m walls, about 5.5 litres of emulsion for two coats on the walls.
How far does a litre of paint go?
Most emulsions cover about 10 to 13 m² per litre per coat on smooth, sealed walls. Rough or new surfaces need more.
Should I buy 2.5 or 5 litre tins?
Buy enough from the same batch to finish the job. Larger tins are usually cheaper per litre.
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Last updated October 2026.