Working out paint quantities isn’t complicated, and getting it right means one trip to the store and no half-finished wall. Here’s the quick method we use at the counter.
- 1
Measure the walls
Measure the length of each wall and multiply by its height to get the area in square metres. Add the walls together. Subtract large openings like big windows and doors; small windows you can leave in as a bit of safety margin.
- 2
Check the coverage rate
Every tin states its spreading rate, usually somewhere around 6 to 8 square metres per litre per coat on a smooth, sealed wall. Rough, porous or unpainted surfaces cover less, so use the lower end for those.
- 3
Do the maths
Divide your total area by the coverage rate, then multiply by the number of coats. Most jobs need two coats. That gives you the litres of topcoat.
- 4
Add primer and a little spare
If the surface needs priming, work that out the same way as a separate product. Then add roughly ten percent overall for touch-ups and the odd thirsty patch.
A worked example
Say a room has 40 m² of wall after subtracting the door and window. At 7 m² per litre that’s about 5.7 litres per coat, so roughly 11.4 litres for two coats. Round up and add a little spare, and a 20-litre would comfortably do the room with paint left for touch-ups.
Rough coverage at a glance
| Surface | Roughly covers | Note |
|---|---|---|
| Smooth, sealed wall | 7–8 m² / litre | Best case, previously painted |
| New or porous plaster | 5–6 m² / litre | Prime first, it drinks paint |
| Rough / textured | 4–6 m² / litre | Texture adds surface area |
| Face-brick | 4–5 m² / litre | Very thirsty, seal it first |
Tip
Going from a dark wall to a light colour, or covering strong stains, usually needs an extra coat or a good primer. Factor that in before you buy.
Bring your measurements to the counter and we’ll size the job for you on the spot, primer, topcoat and the right tin sizes, so you leave with exactly what you need.
Need a hand with your project?
Bring your questions to either store and we’ll match the right products to the job, and work out exactly what you need.
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