Paint Calculator
Work out how much paint you need for a room. Enter the dimensions, coats and paint type for an instant estimate.
Assumes doors ~1.8 m² and windows ~1.4 m² each. Coverage varies by brand, colour and surface. Buy a little extra so the whole room comes from one batch.
Running a builders merchant? OptiFlow answers product and quantity questions like these for your trade customers automatically, 24/7, on top of your existing systems.
See OptiFlow Merchant →Estimate only, always confirm quantities with your merchant before ordering.
How to use the paint calculator
Enter the wall or ceiling area, choose how many coats you are applying, and the calculator works out how many litres of paint you need, allowing for the paint's spreading rate. As a guide, one litre of emulsion covers roughly 10, 12 m² per coat on a smooth, previously painted surface. Bare plaster, masonry and textured surfaces are thirstier, so add a margin for them.
Frequently asked questions
How much paint do I need per m²?
As a rule of thumb, one litre covers about 10, 12 m² per coat on smooth walls. Divide your total area by the coverage figure on the tin, then multiply by the number of coats.
How many coats of paint should I apply?
Two coats is standard for a durable, even finish. Bold colour changes or bare plaster, which needs a thinned mist coat first, can need more.
Does the surface change how much paint I need?
Yes. Bare plaster, masonry, wood and textured surfaces absorb more than a previously painted smooth wall, so add roughly 10, 20% on porous surfaces.