Paint Calculator
Estimate the paint area and volume you need for a room, based on dimensions or a total wall area.
How this is calculated
Wall area (from dimensions) = 2 × (length + width) × wall height. Doors and windows are deducted at 20 ft² and 15 ft² each by default. Paint area = net wall area × number of coats. Gallons = paint area ÷ coverage rate (default 400 ft² per US gallon, roughly 10 m² per litre).
This is an estimate — actual coverage varies by paint and surface.
Frequently asked questions
Should I subtract doors and windows?
Yes, for a more accurate estimate. Each door and window field deducts a standard average area; adjust the counts to match your room, or leave them at 0 if you'd rather round up.
What coverage rate should I use?
Check the paint can label — it usually states coverage in ft² per gallon or m² per litre. The default of 400 ft²/gallon is typical for a mid-sheen wall paint on primed drywall.
How many coats do most walls need?
Two coats is standard for a colour change or full repaint. A single coat may be enough for touch-ups or when applying the same colour.
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