Paint Calculator
Litres = wall area × coats ÷ coverage — enter the area, the number of coats and the paint's spread rate per litre.
Reviewed by the OmniCalc teamMethod verified 2026-07-01
4L
Paint 4 L, buy at least 4 tinsBuy at least 4 tins (1 L each).
Show steps
- Litres = area × coats ÷ coverage = 20 m² × 2 ÷ 10 m²/L = 4 L.
- Round up to whole 1 L tins: ceil(4) = 4 tins.
How to use the paint calculator
- 1Enter the wall area in square metres (m²).
- 2Set the number of coats and the coverage — how many m² one litre covers (printed on the tin).
- 3Read the litres needed and how many tins to buy, with the working under Show steps.
Subtract doors and windows first
The wall area should count only the surface you actually paint. Measure the whole wall, then subtract the area of any doors and windows— they aren’t painted, and leaving them in makes you buy more paint than you need.
Frequently asked questions
How much paint do I need?
Multiply the wall area by the number of coats and divide by the coverage (m² per litre): litres = area × coats ÷ coverage. A 20 m² wall in 2 coats at 10 m²/L needs 4 litres.
What coverage should I use?
Most emulsion and wall paints spread about 10–12 m² per litre per coat, but the exact figure is printed on the tin. Rough or porous surfaces cover less, so use the lower end and round up.
Why does it round up to whole tins?
Paint is sold in whole tins, so the result rounds the litres up to the next whole 1 L tin as a 'buy at least' hint. Keep the leftover for touch-ups — colours are hard to match later.