Enter your wall area to find how many gallons of paint you need. One gallon covers about 350 ft² per coat, so most rooms take one to two gallons for two coats after subtracting doors and windows.
You need approximately
1 gallon
covers 336 ft² (incl. waste)
Area to cover
336 ft²
Exact amount
0.96 gallons
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Field notes
Always calculate for the coats you'll actually apply — nearly every color change needs two, and primer is a separate gallon on bare drywall or a big color jump. The 350 ft²/gallon spread rate assumes primed, smooth walls; textured or porous surfaces drink more, so round up. Box your paint (combine cans into one bucket) so the color stays consistent wall to wall.
Multiply the room perimeter by the wall height for total area, subtract doors and windows, then divide by 350 ft² per gallon and multiply by the number of coats. A 12×12 room usually needs about 2 gallons for two coats.
How many square feet does a gallon of paint cover?
One gallon of interior paint covers about 350–400 ft² in a single coat on primed, smooth walls; textured or porous surfaces cover less.