Paint Calculator — How Much Paint You Need
Estimate how many gallons or litres of paint a room needs from wall size, doors, windows and coats. Metric or imperial, free, in your browser.
🔒 Calculated in your browser. Coverage and opening sizes are editable defaults — real coverage varies with surface, colour and primer. Round up when buying.
How much paint to buy
Enter your wall perimeter and height, the number of doors and windows to subtract, and the number of coats. The tool works out the paintable area and how much paint that needs at the coverage rate (default ~350 sq ft per gallon or ~10 m² per litre), then rounds up to whole cans.
Keep the defaults honest
Real coverage varies with the surface, colour change and primer, so the coverage and opening sizes are editable defaults, not fixed truths. When in doubt, buy a little extra for touch-ups. Everything is calculated in your browser.
Frequently asked questions
How much does a gallon of paint cover?
Roughly 350 square feet (about 32 m²) for one coat on a smooth, primed wall. Rough or unprimed surfaces need more, so adjust the coverage field.
How many coats should I plan for?
Two coats is typical for good coverage and colour changes. One coat may do for repainting a similar colour. The tool multiplies by whatever you enter.