Formula
Openings are removed before the coats are applied:
amount = (area − openings) × coats / coverage
Square feet pair with gallons. Square meters pair with liters. The page rounds the exact amount to two decimals and rounds the container count up.
Assumptions
- Area and coverage use the unit system you select.
- Each coat uses the same coverage.
- Primer is a separate coat only if you include it in the coat count.
Worked example
400 square feet, no openings, and 2 coats at 350 square feet per gallon use 2.29 gal.
Input definitions
- Area
- Walls or ceiling you intend to paint, before subtracting doors and windows.
- Coverage
- Area one gallon or liter covers, as printed on that can.
Limitations
Rough surfaces, dark colors, and thick nap can use more paint than the can's smooth-surface figure. Wallpaper and flooring are different jobs and are not estimated here.
Questions
Should I buy the exact amount?
Buy the next whole container. The exact figure can leave you short if the last coat runs long.
Does this estimate tile or carpet?
No. The tile page counts tiles and the carpet page reports square yards. This page is only paint coverage.