Paint Calculator

How much paint do I need?

Measure your wall area, subtract doors and windows, then divide by the coverage rate on the tin. Multiply by the number of coats and you've got your answer. That's all this calculator does, just quicker than doing it on the back of an envelope.

What is coverage rate?

Coverage rate is how many square metres one litre of paint will cover on a smooth, sealed surface. Most emulsions sit around 12 m² per litre, but it varies. Bare plaster soaks up more, textured surfaces need more, and a dark colour over a light base might need an extra coat. Always check the tin, but 12 m²/litre is a solid starting point.

How many coats?

Two coats is standard for a good, even finish. You can sometimes get away with one coat if you're going like-for-like on colour, but two is the safe bet. Going from a dark wall to a light colour? You might want three, or use a stain-blocking primer first.

Door and window deductions

The calculator uses 1.9 m² for a standard door and 1.4 m² for a standard window. These are typical UK sizes. If yours are significantly different, you can adjust the count and the calculator will scale accordingly. It's always better to have a bit left over than to run short halfway through a wall.