Paint Calculator
How much paint you need — before you buy the wrong amount.
Wall area to paint:
Gallons needed:
How to use this calculator
Enter room dimensions, wall height, coats of paint, and the window and door areas, then press Calculate. The wall area to paint and gallons needed are shown.
Worked example
A 12 ft by 10 ft room with 8 ft walls has a perimeter of 44 ft and 352 sq ft of wall. Subtract a 21 sq ft door and a 15 sq ft window leaves about 316 sq ft. A gallon covers roughly 350 sq ft per coat, so two coats need about 1.8 gallons - meaning two gallons with a little to spare for touch-ups.
What the result means
The tool returns the gallons needed for the coats you entered. Ceilings, trim and doors are separate surfaces - this figure covers the walls only, so add those jobs to your total.
Why the waste fields are there
- Windows and doors subtract paintable area - leaving them out overbuys by a coat's worth on big rooms.
- Roller application soaks up more paint than spraying, and dark-over-light covers need more coats.
- Paint sheen and brand coverage vary, so check the label's sq ft per gallon before you finalize.
Frequently asked questions
Do I really need two coats?
Over most primed or similar-colored walls, yes - two coats give even color and durability. A third is only for dramatic color changes.