Gallons of paint for a room, with doors, windows and coats.
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How do you calculate how much paint you need?
A typical 12x10 ft bedroom with 8 ft walls needs about 1.74 gallons of paint for two coats, so buy 2 gallons.
Wall area is the room's perimeter times the wall height. We subtract 21 sq ft for each door and 15 sq ft for each window, add the ceiling if you include it, multiply by the number of coats, add 10% for touch-ups, and divide by your surface's coverage per gallon. To buy, we round up to whole gallons, adding 1 or 2 quarts when that covers the rest: 3 quarts usually cost more than a gallon.
Frequently asked questions
How much paint do I need for a 12x12 room?
With 8 ft walls, one door, one window and two coats, a 12x12 room needs about 2 gallons of paint for the walls.
How many square feet does a gallon of paint cover?
About 350 to 400 sq ft per coat on smooth, previously painted walls; closer to 300 sq ft on new drywall or textured walls, and 200 sq ft on brick or stucco.
Do I need two coats of paint?
Usually yes. Plan two coats when changing color, painting over a darker color or painting new drywall. One coat can be enough when refreshing the same color.
Do I need primer before painting?
Use primer on new drywall, bare wood, patched spots, and when covering a dark color with a light one. On clean walls that are already painted a similar color, two coats of paint are usually enough.
How much paint do I need for a ceiling?
A 12x10 ft ceiling is 120 sq ft. Two coats with 10% extra need about 0.66 gallon at 400 sq ft per gallon, so buy one gallon: it usually costs less than 3 quarts.