How the estimate works
Paintable area = total wall area − openings. Paint volume = paintable area × coats ÷ coverage per unit.
Assumptions and limits
Coverage varies by product and surface texture. Round purchase quantity up; actual needs can differ with preparation and application.
Example
Four walls measuring 4 m × 2.5 m each have 40 m² gross area. Subtract 4 m² of openings; at 10 m²/L for two coats, the estimate is 7.2 L before waste.