Paint Coverage Calculator
Calculate gallons of paint needed for any room, accounting for doors, windows, and number of coats.
Enter room dimensions, openings, and paint specs. Returns total gallons needed and rounded-up purchase quantity.
Room dimensions
Subtract openings
Paint
How wall area is calculated
Room perimeter (2 * length + 2 * width) times ceiling height gives gross wall area. Subtract approximate openings: doors at 21 sq ft each (standard 3x7 ft) and windows at 15 sq ft each (typical 3x5 ft). Result is the actual paintable wall area.
Paint coverage
Most interior latex paints cover about 350 sq ft per gallon on smooth, primed walls. Coverage drops for porous or rough surfaces (textured walls, raw drywall, brick): assume 250 sq ft per gallon. Dark colors over light usually need 2 coats; light over light may need only 1; light over dark needs 2-3 coats plus possibly a primer.
Always round up when buying
Stores sell paint in gallons and quarts, not fractional gallons. Always buy at least the rounded-up whole number, plus 10-15 percent extra for touch-ups, drips, and miscalculations. Keep leftover paint sealed for future repairs; properly stored paint lasts 2-10 years.
What this calculator does NOT include
- Ceiling paint (calculate separately as length x width)
- Trim paint (typically half a gallon to a gallon for a whole room)
- Primer (when needed, usually one coat covers 200-300 sq ft per gallon)
- Texture or rough surfaces (lower coverage; adjust the per-gallon coverage downward)