How it is calculated
Coverage defaults to 10 m² per litre for one coat. The tin often prints a range. Use the smaller figure for a dark colour over a light one, and for a textured wall.
Litres = (walls − openings) × coats / coverage × (1 + waste)
Where the numbers come from
- Wall area — unit in the field: m²
- Windows and doors — unit in the field: m²
- Layers
- How many m² one liter covers — unit in the field: m²/L
- Waste — unit in the field: %
Example
40 m² of walls, 5 m² of openings, two coats, 10 m² per litre. Paint 35 m² × 2 / 10 = 7 L; with 10% waste, 7,7 L.
Questions
Is primer included?
No. Only the paint is counted. Primer usually has its own coverage rate.
Should I add the ceiling?
Yes, if you paint it with the same paint: include those metres in the area.
Why cans of 2,5 L?
A common can size for interior paint. If yours is different, divide the litres by the volume of your can.