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.