Coverage
The default 350 ft² per gallon follows the lower end of Sherwin-Williams' typical 350–400 ft² range. Replace it with your product label. Source
Paint / material estimate
Paint calculator
Estimate walls and an optional ceiling, then account for openings, coats, coverage, waste, and the price on your paint can.
The assumptions are part of the answer.
Openings
Standard openings use 21 ft² per door and 12 ft² per window. Unusual openings should be adjusted by changing the room estimate conservatively.
Before you buy
Three checks that prevent a second trip.
Use the label coverage
Primer, textured walls, porous surfaces, and dramatic color changes can reduce real coverage.
Count every coat
The estimate multiplies the prepared surface by your coat count before adding the extra allowance.
Keep the batch consistent
Buy the project quantity together and box multiple cans before painting for more consistent color.