How to Calculate Paint Coverage: What the Tin Doesn't Tell You

Paint tins give you a coverage estimate, but it's rarely the whole story. Learn what affects paint coverage and how to get an accurate calculation for your UK home.

7/13/20262 min read

When you pick up a tin of paint, you'll usually find a coverage rate printed on the label — something like "covers up to 12 sq m per litre". But experienced decorators know this figure is often optimistic. Here's what you actually need to know to calculate paint coverage accurately.

What Does Coverage Rate Mean?

The coverage rate tells you how much surface area one litre of paint can cover in a single coat under ideal conditions. Ideal conditions typically mean a smooth, previously painted surface with a similar base colour. In practice, your walls may not be ideal.

Factors That Reduce Paint Coverage

Several things can mean you'll use more paint than the tin suggests:

Porous surfaces: Fresh plaster, bare brick, or unpainted MDF absorb significantly more paint. You may use 30 to 50 percent more paint on a first coat over porous surfaces.

Dark to light colour changes: Going from a dark colour to a light one almost always requires an extra coat or two. The same applies in reverse if you're painting over a bright colour.

Rolled vs brushed: Rollers typically apply paint more evenly and with better coverage than brushes. If you're brushing an entire wall, factor in slightly more paint.

Wall texture: Textured or rough walls have more surface area than smooth ones. Artex ceilings and pebbledash walls can require significantly more paint.

How to Get an Accurate Coverage Calculation

1. Measure your total wall or ceiling area in square metres.

2. Look at the coverage rate on your chosen paint tin.

3. Divide area by coverage rate to get litres needed per coat.

4. Multiply by the number of coats.

5. Add a 10 percent buffer for wastage, touch-ups, and second coats.

Example: You have 30 sq m of wall area. Your paint covers 10 sq m per litre. For two coats: (30 ÷ 10) x 2 = 6 litres. Add 10 percent: 6.6 litres. Buy a 5 litre tin and a 2.5 litre tin to cover this comfortably.

When to Use a Paint Calculator

Rather than working this out manually every time, use our free UK Paint Calculator. It accounts for your specific room dimensions, number of coats, and paint coverage rate — giving you a reliable figure in seconds.