Paint Calculator
Estimate how much paint a wall area needs from the coverage on the tin and the number of coats.
Worked example
A room 4 m by 3 m with walls 2.5 m high has 2 × (4 + 3) × 2.5 = 35 m² of wall. Leaving out 5 m² for a door and a window gives 30 m². Two coats cover 60 m², and at 10 m² for each litre that needs 6 litres.
How we calculated this
The four walls of a room add up to twice the length plus the width, multiplied by the wall height. Doors and windows are taken off only if you enter their area. The area to cover is that paintable area multiplied by the number of coats, and the paint needed is the area to cover divided by the coverage you enter. If you choose an allowance, it is added to that result and shown separately.
A result written as a plain number is exact. A result starting with “≈” has been rounded to 10 significant figures, because its exact decimal never ends or is too long to read comfortably. When an exact value is long, its full digits are shown underneath. The calculation itself is never rounded: only the display is.
What this result means
The result is the volume of paint needed to cover the paintable area for the number of coats, at the coverage you entered.
Common mistakes
- Using a coverage figure for a different product. Check the tin for the coverage that applies to your paint and surface.
- Forgetting that every coat needs its own paint. Two coats need twice the paint of one.
Assumptions and limitations
- It is an estimate, not a guarantee. Rough, dark or very absorbent surfaces can use more paint, and the figure is not rounded up to whole tins.
- Ceilings, skirting boards, trim and primer are not included unless you add them yourself.