Paint calculator

Enter the room size and how many coats you plan. The result rounds up to whole gallons and quarts so you don't run short mid-wall.

Room length (ft)

Room width (ft)

Wall height (ft)

Doors

Windows

Coats

Coverage per gallon (sq ft)

Paint the ceiling too?

How the estimate works

Wall area is the room's perimeter times its height. Each door subtracts 21 sq ft (a standard 3 × 7 ft door) and each window 15 sq ft (3 × 5 ft). The paintable area is multiplied by the number of coats, then divided by the coverage figure.

Most interior paints list coverage between 250 and 400 sq ft per gallon. 350 is a common middle value; check your can's label and lower the number for textured walls, fresh drywall, or a big color change.

Tips before you buy

New drywall or a dark-to-light change usually needs primer plus two coats.
Buy all your paint at once from the same batch so the color matches.
A quart covers roughly a quarter of what a gallon does, so leftovers of under a quarter gallon can be bought as quarts.