Paint calculator
Wall area minus doors and windows, times the number of coats, divided by the coverage on the tin.
- Runs in your browser — nothing you enter is uploaded
- No sign-up, no quotas, free to use as often as you like
How it works
Running out of paint two thirds of the way along a wall is worse than buying slightly too much, because the second tin rarely matches the first exactly. Measuring first takes two minutes.
Measure the perimeter, not each wall
Add the lengths of all the walls you are painting and enter that as one number, then the ceiling height. Perimeter times height is the gross wall area, which is quicker and less error-prone than measuring four walls separately.
Doors and windows
A standard door is deducted at about 1.8 square metres and a window at about 1.44. Those are averages — if your windows are unusually large, take the area off the perimeter calculation yourself for a closer figure.
Coverage varies more than you think
The figure on the tin, usually 10 to 13 square metres per litre, assumes a smooth, sealed, previously painted surface. Bare plaster, textured walls and dark colours being covered with light ones all absorb considerably more, sometimes half again. Use the tin's number and buy the next size up.
Coats
Two is standard. Assume three when going light over dark, when covering a strong colour, or on new plaster where the first coat is largely absorbed.
Paint calculator — questions
How much does a litre of paint cover?
Typically 10 to 13 square metres on a smooth sealed surface. Bare plaster and textured walls take considerably more.
Does it include the ceiling?
No. Calculate the ceiling separately as its own area — the room's length times its width.
How many coats do I need?
Two for most repaints. Three when going light over dark or painting new plaster.
Should I round up?
Yes. Buy the next tin size up — a second batch of the same colour will not always match exactly.
Can I work in feet?
Yes. Choose feet and the result is given in both litres and US gallons.