Paint calculator
Enter the wall area in m², the number of coats, the coverage per litre and any doors and windows to deduct, and see the litres and tins to buy.
Estimates only. Check the manufacturer's coverage rates.
How this is calculated
Paint coverage is quoted in square metres per litre for one coat. The calculator takes the wall area, subtracts any openings such as doors and windows, multiplies by the number of coats and divides by the coverage: litres = (wall area - openings) x coats / coverage.
The default coverage is 12 m² per litre, a typical figure for emulsion. It varies with the product and the surface, and porous or new surfaces need more paint, so check the tin and enter its stated coverage.
For example, 40 m² of wall with two coats at 12 m² per litre needs 40 x 2 / 12 = 6.67 litres.
To suggest tins, the calculator looks at combinations of 5 litre and 2.5 litre tins, picks the one with the smallest total volume that still covers what you need, and then the one with the fewest tins. For 6.67 litres that is 1 x 5L + 1 x 2.5L, or 7.5 litres in total. To measure a wall, multiply its length by its height and add the walls together; use the openings box to take off doors and windows.
- 12 m² per litre is a typical emulsion coverage and varies with product and surface. Porous or new surfaces need more.
- Deduct doors and windows with the openings box.
Frequently asked questions
How much does a litre of paint cover?
A typical emulsion covers about 12 m² per litre per coat, but it varies with the product and surface. Check the tin.
Do I subtract doors and windows?
Yes. Enter their area in the openings box and it is deducted before the litres are worked out.
Why do new walls need more paint?
Porous or new surfaces soak up more paint, so coverage per litre is lower.