Common Mistakes When Painting a Room (UK): How Many Litres
Paint tins are labelled for one coat, which is where most people go wrong. A 4 × 3 m room with 2.4 m walls, one door and one window needs about 5.1 litres for two coats at 12 m² per litre. Put your own sizes into the paint calculator.
Mistake 1: buying for one coat
Walls need two coats in most rooms. Litres for the walls of the example:
| Coats | Litres |
|---|---|
| 1 | 2.5 L |
| 2 | 5.1 L |
| 3 | 7.6 L |
Mistake 2: leaving out the ceiling
The ceiling is the same area as the floor. Litres for two coats by room size:
| Room | Walls only | Walls and ceiling |
|---|---|---|
| 3 × 3 m | 4.3 L | 5.8 L |
| 4 × 3 m | 5.1 L | 7.1 L |
| 4 × 4 m | 5.9 L | 8.5 L |
| 5 × 4 m | 6.7 L | 10.0 L |
| 6 × 5 m | 8.3 L | 13.3 L |
Mistake 3: believing the coverage on the tin
Coverage is quoted for a smooth, sealed wall. Rough or porous surfaces soak it up. For the example room:
| Coverage | Walls only | Walls and ceiling |
|---|---|---|
| 10 m² per litre | 6.1 L | 8.5 L |
| 12 m² per litre | 5.1 L | 7.1 L |
| 13 m² per litre | 4.7 L | 6.5 L |
| 14 m² per litre | 4.4 L | 6.1 L |
Mistake 4: counting the openings oddly
Doors and windows take only a little off the total:
| Openings | Litres for walls |
|---|---|
| 0 doors, 0 windows | 5.6 L |
| 1 door, 1 window | 5.1 L |
| 1 door, 2 windows | 4.8 L |
| 2 doors, 3 windows | 4.3 L |
Mistake 5: skipping the prep
- Fill and sand, then wipe off the dust so the paint can bond.
- Mist-coat new plaster with watered-down emulsion, and use primer on stains and bare wood.
- Cut in at the edges, then roll before the edge dries, and keep a wet edge.
- Mix several tins together in one bucket to avoid slight colour differences.
For brushes, rollers and primer on one list use the room decorating materials calculator. Estimates only.
Frequently asked questions
How much paint for a 4 × 3 m room?
With 2.4 m walls, one door, one window and two coats, about 5.1 litres for the walls. With the ceiling it is 7.1 litres.
Do I need two coats?
For a colour change or new plaster, yes. Mist-coat new plaster, and use a primer on stains.
Can I use wall paint on the ceiling?
Better to use a ceiling paint. It is thicker so it spatters less, and it is made for the job. Count it separately.
Should I buy extra?
A little for touching up. Buy it all at the same time, from the same batch, so that the colour matches.
More guides
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and check the Building Regulations and any planning rules for anything structural or close to a boundary.