Paint Calculator
Free paint calculator: how much paint a room needs from its size, doors and windows, number of coats and coverage, in litres or gallons, plus the cans.
Also: Tile Calculator · Flooring Calculator · Square Footage Calculator
What it does
The calculator adds up the four walls of the room (twice the length plus the width, times the height), takes off a standard door (1.8 m², 21 ft²) and window (1.5 m², 15 ft²) for each one, adds the ceiling if you want, and multiplies by the number of coats. Coverage is printed on the can: about 10 m² per litre or 350–400 ft² per gallon for most wall paints.
How to use it
- Enter the length, width and height of the room, and how many doors and windows it has.
- Set the number of coats and the coverage from the can; tick the ceiling if you are painting it.
- Choose the can size to see how many cans to buy.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked questions
How many coats of paint do I need?
Two coats is the usual rule for an even finish, especially when changing colour. One coat can be enough when repainting the same colour, and new plaster or a much darker old colour may need a primer first.
Why buy a little more than calculated?
Rough or porous walls absorb more paint than the coverage on the can, and a spare amount of the same batch is useful for touch-ups later.