Paint Calculator
Enter the area, coats and the coverage printed on the tin to get litres and cans.
The formula
Litres = area × coats ÷ coverage (m²/L). Coverage is on the label, usually 8–14 m²/L per coat.
Worked example
A 4 × 5 m room with a 2.7 m ceiling has an 18 m perimeter and 48.6 m² of wall. Minus a door and a window it is 44 m². Two coats at 10 m²/L: 44 × 2 ÷ 10 = 8.8 L — three 3 L tins or one 10 L tin with a little left over.
Why you always use more than the label says
- The substrate drinks it. Fresh filler, gypsum plaster and aerated block soak up paint. Primer saves more paint than it costs.
- Colour change. Dark over light, or the reverse, almost always means a third coat.
- Tools. A long-pile roller holds more paint than a short one, and a sprayer loses paint to overspray.
How many coats you really need
| Situation | Coats |
|---|---|
| Primed fresh filler, same colour | 2 |
| Repainting a similar shade | 1–2 |
| Changing to a contrasting colour | 2–3 |
| Plasterboard with no primer | 3 or more |
Buy paint from one batch and box the tins together before starting: even factory tinting can differ by half a shade.
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