What this calculator does
Use the paint calculator to estimate how many litres you need for a room. It accounts for room dimensions, openings, number of coats and paint coverage.
Formula used
Wall area equals room perimeter multiplied by wall height, minus doors and windows. Paint needed equals paintable area multiplied by coats, divided by coverage per litre.
How to read the result
Round up before buying, especially for textured walls, strong colour changes or touch-ups. Paint coverage varies by product and surface.
Assumptions
- Assumes a rectangular room.
- Does not include ceiling paint unless you add that area manually.
- Uses the coverage value printed on your paint tin.
Sources and checks
This calculator uses a standard public formula. Where rules or thresholds can change, source links are listed on the relevant page.
Frequently asked questions
Should I buy exactly the calculated amount?
Usually no. Round up so you have enough for touch-ups, waste and surface variation.