Paint Calculator
Estimate the gallons of paint for a room, accounting for coats, doors, and windows.
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How it works
Wall area is the room perimeter times the wall height. Subtract about 21 sq ft per door and 15 sq ft per window, multiply by the number of coats, then divide by the paint’s coverage rate (about 350 sq ft per gallon).
Formula
Gallons = (Wall area − openings) × coats ÷ coverage per gallon
Frequently asked questions
How much does a gallon of paint cover?
About 350 square feet per coat on smooth walls. Textured or porous surfaces may only get 250–300.
How many gallons to paint a 12x12 room?
A 12×12 room with 8 ft walls needs roughly 2 gallons for two coats after subtracting a door and two windows.
Do I need primer?
Use primer on new drywall, bare wood, or when making a big color change. Otherwise a quality paint-and-primer usually suffices.