Paint calculator
Gallons needed for a room, coats included.
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How it's calculated
Wall area is the room perimeter times the wall height, less about 20 square feet per door and 15 per window, since those are not painted. Multiply by the number of coats and divide by the coverage on the can, usually 350 to 400 square feet per gallon. The ceiling is length times width. Round up, and keep some for touch-ups.
How many coats do I need?
Two for most colour changes and for a durable finish. One can do when repainting the same colour in good condition. Going from dark to light, or painting fresh drywall, plan on primer plus two coats.
Should I buy a gallon or quarts?
Round up to whole gallons for the walls; a gallon usually costs less than three quarts. Use quarts for trim and small touch-ups. Leftover paint from the same can keeps touch-ups matching.
Does the calculator include trim and doors?
No. Trim, doors and windows are usually painted a different sheen or colour. A quart covers about 90 square feet, enough for the trim in an average room.
Results are estimates for informational purposes only and are not financial, medical or legal advice.