How it is calculated
- Wall area = room perimeter × height = 2 × (length + width) × height.
- Subtract doors (≈ 2 m² each) and windows (≈ 1.5 m² each).
- Paint = area × coats ÷ coverage per litre (typically 10–12 m² per litre per coat), plus 10% spare.
Worked example
A 4 × 3.5 m room, 2.8 m high, with one door and two windows, two coats: walls = 42 m² − 5 = 37 m²; paint = 37 × 2 ÷ 10 ≈ 7.4 L + 10% = 8.1 L, i.e. three 4-litre cans.
Frequently asked questions
How many coats?
Usually two; three when going from dark to light, plus a primer on new walls.
What is the coverage?
It is printed on the can, typically 8–14 m² per litre depending on paint and surface.
Should I include the ceiling?
Tick the ceiling option to add length × width.