Paint Calculator
Calculate gallons of paint needed for a room based on wall area, number of doors and windows, and coat count. Assumes 350 sq ft per gallon coverage.
Results
What is it?
The Paint Calculator estimates the number of gallons of paint needed to cover the walls of a room. It deducts standard door and window areas from the total wall surface and multiplies by the number of coats, using the industry standard of 350 sq ft per gallon.
How to use
1. Measure and enter room length, width, and ceiling height. 2. Enter the number of doors and windows. 3. Select the number of coats (2 is standard; primer + 2 finish coats requires a separate primer calculation). 4. The calculator rounds up to whole gallons — always buy at least one extra quart for touch-ups.
Example scenario
A 15 × 12 ft living room with 9 ft ceilings, 1 door, and 3 windows, painted with 2 coats: net wall area = 2×(15+12)×9 − 21 − 45 = 486 − 66 = 420 ft². Paintable area = 840 ft². Gallons = ceil(840/350) = 3 gallons.
Pro tip
Dark or saturated colors often require a tinted primer to reduce the number of topcoats needed. A 5-gallon bucket is cheaper per ounce than five 1-gallon cans. Keep the leftover paint sealed and labeled — you'll need it for touch-ups within the year.