How Does It Work?
- Measure the roomLength, width and wall height. The calculator works out the perimeter and multiplies by the height, so you do not need to measure each wall separately.
- Subtract the openingsEach door is treated as about 1.8 m² and each window as about 1.5 m². Standard sizes, but adjust the count if yours are unusually large.
- Choose coats and coverageTwo coats is normal. Coverage is printed on the tin — use that figure if you have it, since it varies a lot between matt, silk and primer.
What Is It Used For?
Paint is sold in fixed tin sizes, so the useful answer is not "how many litres" but "how many tins". This calculator gives both, deducts doors and windows rather than pretending the walls are blank, and multiplies by the number of coats — which is where most rough estimates go wrong, because two coats on a dark wall is really the minimum.
- Estimating paint for a bedroom, living room or hallway before a trip to the shop.
- Budgeting a whole-house repaint room by room.
- Checking a decorator’s materials quote.
- Working out whether one more tin is needed for a second coat.
- Converting between metric and imperial coverage figures on a tin.
Examples
| Room | Coats | Area to paint | Paint needed |
|---|---|---|---|
| 4.5 × 3.5 × 2.5 m, 1 door, 1 window | 2 | 36.7 m² | 6.7 L (3 × 2.5 L) |
| 3 × 3 × 2.4 m, 1 door, 1 window | 2 | 25.5 m² | 4.6 L (2 × 2.5 L) |
| 5 × 4 × 2.5 m + ceiling, 1 door, 2 windows | 2 | 59.2 m² | 10.8 L (5 × 2.5 L) |
| 12 × 12 × 8 ft, 1 door, 1 window | 2 | 348.5 sq ft | 1.9 gal (2 gallons) |