Paint Calculator
Calculate how much paint you need for walls based on room dimensions.
Results
Buying too much paint wastes money and buying too little means an extra trip to the store mid-project. This paint calculator estimates how many gallons you need based on your room dimensions, automatically subtracting standard door and window areas. It assumes 2 doors (~20 sq ft each) and 2 windows (~15 sq ft each) with standard coverage of 350 sq ft per gallon. For rooms with more or fewer openings, adjust your expectations accordingly.
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Frequently asked questions
One gallon of interior paint covers approximately 350-400 sq ft on smooth walls. Textured walls, porous surfaces and dark-over-light color changes may reduce coverage to around 300 sq ft per gallon.
Two coats is standard for most paint jobs. You may need 3 coats when painting over a dark color with a lighter shade, or when using red or yellow paint which typically have less hiding power.
Buy an extra quart for touch-ups. Keep the same batch because paint colors can vary slightly between manufacturing runs. Store leftover paint in a cool dry place with the lid sealed tightly.
Ceiling area is simply length times width. A 12 x 10 foot room has a 120 sq ft ceiling. At 350 sq ft per gallon, one gallon easily covers a standard room ceiling in two coats.
Primer helps paint adhere and hide better, so you may only need 1 coat of finish paint over a good primer. Without primer, you almost always need 2 coats for even coverage.