Paint Calculator
Find out how many gallons of paint you need for one room or a whole house — accounting for ceilings, doors, windows, and coats. Enter room dimensions or your square footage directly, and add as many rooms as you like for a single combined total.
Paint needed
How the paint calculator works
For every room you add, we calculate the wall area, subtract the space taken up by doors (about 20 sq ft each) and windows (about 15 sq ft each), and add the ceiling (length × width) when you choose to paint it. We sum the paintable area across all your rooms, then multiply the total by your number of coats. One gallon of paint covers roughly 350 square feet per coat.
- Primer: bare drywall or big color changes usually need a primer coat too.
- Dark or bold colors often need an extra coat for full coverage.
- Ceilings: switch the ceiling option to "Also paint the ceiling" to include it automatically.
- Know your area? Switch any room to "Square footage" to enter the paintable area directly — handy for odd-shaped rooms.
Frequently asked questions
How much does a gallon of paint cover?
A gallon covers about 350 square feet in a single coat on smooth walls. Rough or porous surfaces absorb more, so coverage drops.
Do I need one coat or two?
Two coats is standard for an even, durable finish. You may get away with one when repainting a similar color over a primed wall.
Should I buy a little extra?
Yes — keep some for touch-ups. We round up to whole gallons, but a quart of leftover paint is handy after move-in scuffs.