Paint Calculator
Find how much paint you need — enter your room size, ceiling height, number of coats and doors and windows to get the gallons of wall paint (and ceiling), with cost.
How much paint do I need?
Paint is figured from wall area. Multiply the room perimeter by the ceiling height for the wall area, subtract the doors and windows, then multiply by the number of coats and divide by the coverage — about 350 square feet per gallon. The calculator above does this and adds the ceiling if you want it.
gallons = (perimeter × height − openings + ceiling) × coats ÷ 350
Paint by room size (two coats, walls)
| Room | Wall area | Paint (2 coats) |
|---|---|---|
| 10 × 10 ft | ≈ 320 sq ft | ≈ 2 gallons |
| 12 × 12 ft | ≈ 384 sq ft | ≈ 2 gallons |
| 15 × 15 ft | ≈ 480 sq ft | ≈ 3 gallons |
| 20 × 20 ft | ≈ 640 sq ft | ≈ 4 gallons |
At 8-foot ceilings, before subtracting doors and windows. Two coats is standard for an even finish.
Doing the floor or walls too? See the flooring calculator, tile calculator and drywall calculator.
Frequently asked questions
How much paint do I need?
Work out the wall area — the room perimeter times the ceiling height — subtract the doors and windows, then multiply by the number of coats and divide by the coverage (about 350 square feet per gallon). The calculator above does this and rounds up to whole gallons and quarts.
How many gallons does it take to paint a room?
A typical 12×12 room with 8-foot ceilings has about 384 square feet of wall. At one coat that is roughly 1.1 gallons; for two coats plan on about 2 gallons. Add more for the ceiling and any extra coats — enter your room above for an exact figure.
How much does a gallon of paint cover?
One gallon of wall paint covers about 350–400 square feet in a single coat on a smooth, primed surface. Rough, porous or dark-to-light surfaces cover less and often need an extra coat. The calculator uses 350 sq ft per gallon as a practical figure.
How many coats of paint do I need?
Two coats is the standard for an even, durable finish, especially over a new color. One coat can work when repainting a similar color over a primed wall, while big color changes or patchy surfaces may need a primer plus two coats. Set the coats above to match your job.