Paint Calculator
Work out how many litres of paint you need for your walls, with doors and windows deducted. Free, no sign-up.
Written by the Arch.AI team · Maintained by Gio · Updated
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You need about
Wall area 35.9 m² · 1 × 5 L + 1 × 2.5 L
Walls only, ceiling not included. Rough or new plaster needs more paint; check the coverage on the can.
How to calculate how much paint you need
Work out the wall area: the room perimeter (2 × length + 2 × width) times the wall height. A 4 × 3 m room with 2.8 m walls has 39.2 m² of wall.
Subtract doors (about 1.8 m² each) and windows (about 1.5 m² each), then multiply by the number of coats. Two coats is typical.
Divide by the paint's coverage. Interior wall paint usually covers about 10 m² per litre per coat on smooth plaster. The coverage on your can may differ by brand.
Quick estimates for 2 coats
| Room size | 2.8 m walls | Paint needed | Suggested cans |
|---|---|---|---|
| 3 × 3 m (small bedroom) | ≈ 30 m² | ≈ 6.1 L | 1 × 5 L + 1 × 2.5 L |
| 4 × 3 m (bedroom) | ≈ 36 m² | ≈ 7.2 L | 1 × 5 L + 1 × 2.5 L |
| 5 × 4 m (living room) | ≈ 47 m² | ≈ 9.5 L | 1 × 5 L + 2 × 2.5 L |
| 6 × 5 m (family room) | ≈ 58 m² | ≈ 11.7 L | 2 × 5 L + 1 × 2.5 L |
Paint for one wall: common sizes
One wall with no door or window, 2 coats, 10 m² per litre. Multiply the wall's width by its height to get its area.
| Wall size | Area | Paint needed | Suggested cans |
|---|---|---|---|
| 3 × 2.5 m | 7.5 m² | ≈ 1.5 L | 1 × 2.5 L |
| 4 × 2.8 m | 11.2 m² | ≈ 2.3 L | 1 × 2.5 L |
| 5 × 3 m | 15 m² | ≈ 3.0 L | 1 × 2.5 L + 1 × 1 L |
| 10 × 8 ft | 80 sq ft (7.4 m²) | ≈ 1.5 L | 1 × 2.5 L |
| 12 × 8 ft | 96 sq ft (8.9 m²) | ≈ 1.8 L | 1 × 2.5 L |
| 10 × 10 ft | 100 sq ft (9.3 m²) | ≈ 1.9 L | 1 × 2.5 L |
| 12 × 12 ft | 144 sq ft (13.4 m²) | ≈ 2.7 L | 1 × 2.5 L + 1 × 1 L |
Frequently asked questions
How many coats do I need?
Usually two. Going from a dark colour to a light one, or painting new plaster, may need three coats or a primer first.
How much paint do I need for one wall?
Multiply the wall's length by its height. A 4 m wall that is 2.8 m high is 11.2 m². For 2 coats at a coverage of 10 m² per litre you need about 2.3 litres, so one 2.5 L can is enough. Subtract any door or window on that wall.
How many m² does 1 litre of paint cover?
About 10 m² for one coat on smooth plaster, or about 5 m² when you apply 2 coats. It varies by brand and paint type, and rough or new plaster absorbs more. The coverage printed on your can is the one to trust; enter it in the calculator's coverage field.
Is the ceiling included?
No. This calculator covers walls only. For the ceiling, multiply the room length by its width and add it as a separate area.
Why might the shop's estimate differ?
Coverage depends on the brand, the paint type and the wall surface. Rough or new plaster absorbs more paint. Change the coverage field to match your can.
Can I see the colour in my room first?
Yes. Arch.AI's wall colour simulation changes the wall colour on a photo of your own room in seconds, while the furniture stays the same.
Need tiles as well? Use the Tile Calculator →
Looking for colour ideas? See Bedroom & Living Room Paint Colours →
Before
After · AISee the colour in your own room
Before you buy paint, try the colour on a photo of your own room. The AI changes the wall colour in seconds.
Try the wall colour simulation →