How this calculator works
Net wall area = room perimeter × wall height − opening area. Paint = net area × coats × waste factor ÷ coverage.
Worked example
For a 4 m × 3 m room with 2.5 m walls, one door, two windows, two coats, 10 m²/L coverage, and 10% waste, the estimate is about 6.67 L, so three 2.5 L containers.
Assumptions to check
- Ceilings and trim are not included.
- Default door and window areas are editable approximations.
- Coverage varies by paint, surface, color change, and application method; use the product label.