Wall paint calculator — square feet & gallons

Calculate paintable wall area, not floor area

For a rectangular room, multiply its perimeter by wall height, then subtract the total area of doors and windows. Add separate rooms before calculating containers when they share one paint colour.

A worked wall-paint example

12 × 10 ft with 8 ft walls: 2 × (12 + 10) × 8 = 352 sq ft of walls. Subtract 20 sq ft of openings to get 332 sq ft. At 350 sq ft per gallon and two coats, the exact estimate is 664 ÷ 350 = 1.897… US gallons. Two one-gallon cans cover that illustrative estimate.

Coverage and coats change the result

Manufacturer ranges use their lower coverage value by default. A quoted “up to” coverage is not a guarantee on every surface. Check porosity, colour change, application method and preparation; adjust the form to your current label.