Paint Calculator
Home & ConstructionWork out how many litres of paint a room needs, and how many cans to buy, before you go shopping.
Runs entirely in your browser — nothing is uploaded
Features
- Paintable wall area with doors and windows deducted.
- Litres for any number of coats and any coverage rate.
- Cans to buy, rounded to the tin sizes actually sold.
- Optional ceiling, and an estimated cost.
- Runs in your browser.
How to use the Paint Calculator
- 1Enter the room dimensions including the ceiling height.
- 2Set how many doors and windows to deduct.
- 3Adjust coats and coverage, then read the number of cans.
Frequently asked questions
How much paint do I need for a room?
Work from wall area, not floor area: perimeter × height, less doors and windows. At a typical 10-12 m² per litre per coat, a 12 × 10 ft room with a 10 ft ceiling needs roughly 7-8 litres for two coats including the ceiling.
How many coats of paint do I need?
Two over an already-painted wall in a similar shade. Three if you are going light over dark, or covering a strong colour. Fresh plaster needs a primer first, which is not paint and is calculated separately.
Why did my paint not cover as far as the tin said?
The coverage on the tin assumes a smooth, sealed, similarly coloured surface. Fresh plaster, textured walls, rollers over brickwork and dark-to-light changes all drink far more. Buy slightly over rather than matching a batch later — the same shade varies between production runs.