🎨 Paint Calculator
Add up the length of all the walls you are painting, enter the wall height, and the number of doors and windows.
How the Paint Calculator works
Wall area is total wall length × height, minus about 20 ft² per door and 15 ft² per window. It is multiplied by the number of coats and divided by the paint's coverage (often 350–400 ft² per gallon — check the can).
Step-by-step calculation
- 1Add up wall lengths and multiply by height.
- 2Subtract doors and windows.
- 3Multiply by coats.
- 4Divide by coverage per gallon.
Worked example
Walls totaling 48 ft long and 8 ft high with 1 door and 2 windows: 384 − 20 − 30 = 334 ft². Two coats at 350 ft²/gal need 1.91 gallons — buy 2 gallons.
Paint Calculator examples
| Total wall length (ft) | Paint needed |
|---|---|
| 24 | 0.81 gallons |
| 36 | 1.36 gallons |
| 48 | 1.91 gallons |
| 60 | 2.46 gallons |
| 72 | 3.01 gallons |
Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a Paint Calculator?
Buy the right amount of paint for a room.
Important factors that can affect your results
- Rough or porous walls absorb more.
- Color changes may need primer.
- Coverage differs by brand.
Frequently asked questions
Do I need primer?
Use primer on new drywall, bare wood, stains or big color changes.
How do I paint a ceiling?
Multiply room length by width for the ceiling area and add it as a separate job.
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Last reviewed November 2026 · How we build and check our tools · Report a problem