How much paint do I need? Enter your room’s width, length and wall height below and this calculator works out exactly how many litres of paint to buy, plus the tin sizes that make sense. It handles multiple coats, doors and windows, the ceiling, and switches between metres and feet.
Estimate based on typical UK coverage. Buy a little extra for touch-ups and second coats.
How to use the paint calculator
- Enter your room width, length and wall height.
- Set the number of coats (2 is standard for a colour change).
- Subtract doors and windows so you don’t over-buy.
- Tick ceiling if you’re painting that too.
You’ll get the litres needed and a simple “buy this many tins” suggestion.
The formula: how much paint per m²
Paintable area = 2 × (width + length) × wall height, minus about 1.8 m² per door and 1.5 m² per window. Multiply by the number of coats and divide by the paint’s coverage (typically 12 m² per litre for emulsion). We round up so you’re never a few centimetres short.
Frequently asked questions
How much paint do I need for one room?
A typical UK living room (about 3.5 × 4.2 m with 2.4 m walls) needs roughly 5 litres for two coats of emulsion. Use the calculator above for your exact room.
How many coats of paint do I need?
Two coats is standard, especially over a new colour. Repainting the same shade can sometimes need just one.
How much does one litre of paint cover?
Most emulsions cover about 12 m² per litre, per coat. Primers and masonry paints cover a little less (~10 m²); gloss and satin wood a little more (~14 m²).
Should I buy extra paint?
Yes, keep a little for touch-ups and to be sure the second coat has enough. The tin suggestion already rounds up to sensible sizes.