Paint Calculator

Calculate gallons of paint for a room's walls and ceiling, net of doors and windows, plus a primer estimate.

ft²
Most paints cover 350–400 ft² per gallon on smooth walls; rough or porous surfaces use more.

Paint needed

2.1 gal

  • Gallons to buy3 gal
  • Wall area (minus openings)365 ft²
  • Ceiling paint0 gal
  • Primer (1 coat)1 gal

Estimates only. Round up when you order, and confirm structural details with your local building code.

How to use it

  1. Enter room size and wall height.
  2. Enter the number of doors and windows.
  3. Set coats and the coverage printed on the can.

The formula

Wall area = perimeter × height − 21 ft² per door − 15 ft² per window

Gallons = area × coats ÷ coverage

Worked example

Room length14 ft
Room width12 ft
Wall height8 ft
Doors1
Windows2
Coats2
Coverage per gallon350 ft²
Paint ceiling tooNo

Result

Paint needed2.1 gal
Gallons to buy3 gal
Wall area (minus openings)365 ft²
Ceiling paint0 gal
Primer (1 coat)1 gal

Tips before you order

  • Dark colors over light (or vice versa) often need a third coat or a tinted primer.
  • Buy all the paint from one batch, or box (mix) the cans together.

Questions

How much paint for a 12×12 room?

About 2 gallons for two coats on 8 ft walls, without the ceiling.