What is it?
The Paint Calculator tells you how much paint to buy for a room. It works out the area to paint and the litres of paint and primer you need.
Who is it for?
Homeowners repainting rooms, painters quoting jobs, and tenants estimating a fresh coat.
How to use it
- Enter Room length, Room width and Wall height.
- Enter the number of Doors and Windows; tick Paint the ceiling too if needed.
- Set the Coats (2 is normal) and the Coverage of the paint from the tin.
Coverage
Doors counted as 1.9 m² and windows as 1.5 m². Check the coverage on your paint tin: emulsions cover about 8–12 m² per litre per coat. Rough or new plaster walls drink more paint; use the lower figure.
Buying tips
- New walls need primer (and often putty) first. Repainting the same colour may need only one coat.
- Dark to light colours may need an extra coat.
- Buy all paint from the same batch for an even shade, and keep a little for touch-ups.
- Texture and exterior paints have different coverage; check their tins.
Worked example
A 12 × 10 ft room with 10 ft walls has 440 sq ft (about 41 m²) of wall; minus one door and one window, about 37.5 m². Two coats at 10 m² per litre: about 7.5 litres of paint and 4 litres of primer.
Errors and how to fix them
- “Enter the room size (more than 0)”: fill in length, width and height.
Open the tool: Paint Calculator
Still stuck?
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Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.