Paint Calculator — Litres Needed for a Room
Enter the room dimensions and the number of coats to see the wall area and the litres of paint to buy. Avoids the two classic mistakes: running out mid-wall with an unmatchable batch, or buying litres too many.
Paint Calculator
Liters needed to paint a room
How it works
- Typical emulsion covers 10–12 m² per litre per coat.
- Two coats are standard; bare plaster may need three.
- Wall area = perimeter × height; the calculator computes it from length, width and height.
- Buy all tins from the same batch number to guarantee an identical colour.
Worked example: 4 m × 5 m room, 2.6 m walls, two coats
- 1Perimeter: (4 + 5) × 2 = 18 m.
- 2Wall area: 18 × 2.6 = 46.8 m².
- 3Paint: 46.8 × 2 coats ÷ 11 m²/L ≈ 8.5 litres.
≈ 8.5 litres — buy a 10 L tin (or 2 × 5 L)
Paint needed for typical rooms (2 coats, 11 m²/L)
| Room size | Wall height | Wall area | Paint needed |
|---|---|---|---|
| 3 × 3 m | 2.5 m | 30 m² | ≈ 5.5 L |
| 4 × 4 m | 2.5 m | 40 m² | ≈ 7.3 L |
| 4 × 5 m | 2.6 m | 46.8 m² | ≈ 8.5 L |
| 5 × 6 m | 2.6 m | 57.2 m² | ≈ 10.4 L |
Includes walls only. Add the ceiling (length × width) if you are painting it too.
Frequently asked questions
Should I subtract doors and windows?
For small rooms the extra paint is a useful buffer. For large glazed walls, deduct their area from the total before buying.
How many coats of paint do I need?
Two over a similar colour. Going from dark to light, or painting bare plaster or new drywall, usually needs a primer plus two coats.
How much paint do I need for the ceiling?
Ceiling area is length × width. A 4 × 5 m ceiling is 20 m², needing about 3.6 litres for two coats at 11 m² per litre.
Does textured or porous surface need more paint?
Yes — rough plaster, brick and textured wallpaper can use 20–30% more paint than smooth walls. Lower the coverage figure accordingly.
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