🖌️ Construction
Paint Coverage Calculator
Enter the area to paint, the number of coats and the coverage printed on the tin, then press Calculate.
About the Paint Coverage Calculator
Coverage is printed on every tin, usually 10-14 m² per litre for emulsion and 12-16 m² for gloss. New or porous surfaces absorb more, so a first coat on bare plaster can use 30% more than the label promises.
The calculation is area × coats ÷ coverage. A 50 m² room with two coats at 12 m² per litre needs 8.3 litres, which is two 5-litre cans — and buying the second can at the same time avoids a dye-lot mismatch.
How the calculation works
- Litres = area × coats ÷ coverage per litre
- Cans = ceiling(litres ÷ can size)
- Emulsion ≈ 12 m²/L · gloss ≈ 14 m²/L
Reference values
| Area | Coats | Litres at 12 m²/L |
|---|---|---|
| 20 m² | 2 | 3.3 L |
| 35 m² | 2 | 5.8 L |
| 50 m² | 2 | 8.3 L |
| 50 m² | 3 | 12.5 L |
| 80 m² | 2 | 13.3 L |
| 120 m² | 2 | 20.0 L |
Worked examples
- A 45 m² room, two coats, 12 m²/L: 7.5 L, so two 5 L cans.
- A 90 m² room, one coat, 14 m²/L: 6.4 L, so two 5 L cans.
- A 20 m² ceiling, two coats, 12 m²/L: 3.3 L, so one 5 L can with spare.
Where the tin's figure comes from
Coverage is measured on a sealed, non-porous test panel. Bare plaster, fresh plasterboard and previously unpainted wood absorb far more, so the first coat can use 30% additional paint. Prime those surfaces, or budget for the extra litre rather than discovering it halfway through a wall.
Common mistakes
- Forgetting to subtract doors and windows, which are 10-15% of wall area.
- Buying exactly the calculated litres and having none left for touch-ups.
- Changing sheen between coats, which shows as patches under raking light.
A last check on the Area table: 20 m² 2 sits at the base of the chart, and the rows above it step in the same proportion, so you can scale from that first row instead of reading every line. If a figure you were quoted falls between two rows, it is the Coats side that has been rounded, not the conversion itself.