Case 1
- Wall area
- 40m²
- Number of coats
- 2
- Coverage per litre
- 11m²/l
7.27l
Open with these valuesPaint Calculator
7.27l
Result: 7.27 lWall area × coats ÷ coverage per litre. A 40 m² room in two coats with paint covering 11 m² per litre takes 7.27 litres. Coverage is the number that varies most: trade emulsion claims up to 17 m² per litre on a smooth wall, bare plaster swallows far more, so read it off your own tin.
Worked examples
Case 2
- Wall area
- 30m²
- Number of coats
- 1
- Coverage per litre
- 12m²/l
2.50l
Open with these valuesCase 3
- Wall area
- 50m²
- Number of coats
- 3
- Coverage per litre
- 10m²/l
15.00l
Open with these valuesHow it's calculated
litres = wall area × coats ÷ coverage per litre
- StepAdd up the walls: width × height for each, in square metres.
- StepSet the number of coats — two is standard for an even finish.
- StepEnter the coverage printed on the tin, in m² per litre.
- ResultRead the litres; tins come in 2.5 and 5 litres, so round to the tin.
What this number means
Two coats is the normal case
Two coats is the standard for a solid, even finish on interior walls. One may do for a refresh over a similar colour, while a big change of shade can need a third coat or a separate primer.
Coverage varies more than anything else
The trade data sheet behind this calculator states 17 m² per litre on smooth surfaces, and 11 m² is the safer figure for retail emulsion on ordinary walls. Bare plaster swallows far more. Read the number off your own tin.
Litres are not tins
The result is a litre figure and is deliberately not rounded, because tins come in 2.5 and 5 litres. Round it up to the sizes your shop actually stocks.
Commonly misread
Coverage of 11 means 11 litres per square metre.
It is the other way round: one litre covers 11 m². A bigger number therefore means less paint, not more.
The wall area is the area I have to paint.
The area is multiplied by the number of coats before the division. At two coats a 40 m² room is 80 m² of painting, which is 7.27 litres at 11 m² per litre.
Windows and doors are part of the wall, so I leave them in.
Small openings can stay in, and the extra paint becomes useful spare. Take large windows, patio doors or full-height glazing off the wall area first, or you will badly over-buy.
Reference table
| Wall area, coats, coverage | Area to cover | Litres |
|---|---|---|
| 30, 1, 12 | 30 m² | 2.5 |
| 40, 1, 11 | 40 m² | 3.64 |
| 40, 2, 11 | 80 m² | 7.27 |
| 50, 3, 10 | 150 m² | 15 |
| 100, 2, 10 | 200 m² | 20 |
Questions
How much paint do I need?
Multiply the wall area by the number of coats, then divide by the coverage per litre. For a 40 m² room at two coats with paint covering 11 m² per litre, that is 80 ÷ 11, about 7.3 litres.
How do I measure my wall area?
Measure the width and height of each wall and multiply them, then add the walls together. A 4 m by 2.5 m wall is 10 m². Add up every wall you plan to paint and enter the total.
How many coats should I apply?
Two coats is the standard for a solid, even finish on most interior walls. One may do for a refresh over a similar colour, while a big change of shade can need a third coat or a separate primer.
What is coverage per litre and where do I find it?
It is how many square metres one litre covers in a single coat, and it is printed on the tin. The trade data sheet behind this calculator states 17 m² per litre on smooth surfaces; 11 m² is a safer figure for retail emulsion on ordinary walls.
Should I subtract windows and doors?
For small openings it is fine to ignore them — the extra paint becomes useful spare. For large windows, patio doors or full-height glazing, take their area off the wall area first so you do not badly over-buy.
Sources and last check
Information, not professional advice.