How to use
- Enter room length, width and height (or individual walls).
- Subtract doors and windows.
- Set coats and the coverage printed on the can.
Worked example
A 4 × 3.5 m room with 2.5 m walls (37.5 m²), one door (0.9 × 2.1 m) and one window (1.2 × 1.2 m), 3.33 m² of openings in total, and 2 coats at 10 m²/L needs 6.8 L.
Supported formats and limits
| Input | Room size, openings, coats, coverage |
|---|---|
| Output | Paint needed, cans suggestion |
| Engine | Area arithmetic with explicit coverage assumption |
Limitations
- Textured or porous surfaces need more paint than the label coverage.
Questions
How is the amount worked out?
Wall area (plus the ceiling if you include it), minus openings, times the number of coats, divided by the coverage you enter. A 4 x 3.5 m room with 2.5 m walls, one door and one window (3.33 m² of openings), 2 coats at 10 m² per litre, needs 6.8 L.
Why might I need more than the estimate?
The result uses the coverage you type. Textured, porous or freshly plastered surfaces and strong colour changes usually take more paint than the label says, so check the product's data and allow a margin.
Which cans does it suggest?
The smallest purchase that covers the amount, then the fewest cans. In imperial mode it suggests quarts, gallons and 5-gallon pails. Real can sizes vary by brand.
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