Paint Calculator
Enter your room dimensions to estimate how much paint to buy.
What's subtracted from the wall area
This estimate uses a standard door size (~1.85 m²) and window size (~1.5 m²) subtracted from the total perimeter × height figure — measure your actual openings for a more precise result if they're unusually large or small.
About the Paint Calculator
The Paint Calculator estimates how much paint you need for a room from its length, width and wall height, the number of doors and windows, the number of coats and the paint's coverage per litre. It prevents overbuying and last-minute shop trips.
The wall area is the perimeter times height. The area of doors and windows is subtracted, using standard sizes, and the remaining area is multiplied by the number of coats and divided by coverage per litre. Coverage varies by paint and surface, usually ten to twelve square metres per litre. Textured walls and dark colours may need more.
How to use it
- Enter room length, width and wall height in metres.
- Enter the number of doors, windows and coats.
- Enter coverage from the paint tin.
- Read the litres required.
Tips and good to know
- Buy slightly more than needed for touch-ups.
- Primer may be needed on new plaster.
- Ceiling paint is calculated separately.
Frequently asked questions
What coverage should I use?
Check the tin; typical values are 10 to 12 m² per litre.
Does it include the ceiling?
No, only walls.
How many coats?
Two coats are common.