Calculate exactly how much paint you need. Enter your room dimensions and get instant results with waste allowance included.
Painting is one of the most cost-effective ways to refresh a room. But buying too little paint means an extra trip to the store, and buying too much is a waste of money.
The basic formula: Calculate the total wall area (perimeter × height), subtract doors and windows, then divide by the paint's coverage rate (usually 350–400 sq ft per gallon).
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A 12×12 ft room with 8 ft ceilings needs approximately 1-2 gallons of paint for two coats. This assumes standard 2-3 windows and one door. Use our calculator above to get an exact estimate based on your room's dimensions.
Calculate the wall area (perimeter × height), subtract doors and windows, then divide by the paint's coverage rate (typically 350-400 sq ft per gallon). Multiply by the number of coats. Our paint calculator does all this for you automatically.
Painting the ceiling adds 15-20% more area to cover. If you choose to paint the ceiling, check the "Include ceiling" box in our calculator. Ceiling paint is usually flat/matte to hide imperfections.
One gallon of paint covers 350-400 sq ft for one coat. For two coats (recommended), you'll need 1 gallon per 175-200 sq ft. Dark colors or rough surfaces may require more paint.
Primer seals the surface and improves paint adhesion. Use primer on new drywall, bare wood, or when making dramatic color changes. Some paints are "paint + primer" combos, but separate primer often gives better results for challenging surfaces.