Paint Calculator
Gallons, whole cans and cost for room walls and ceiling.
How it works
Paint quantity is surface area times the number of coats, divided by the square-foot coverage printed on the can. The editable 400 ft² per gallon default is a planning rate for one coat, not a promise for every paint or surface.
Bare drywall, masonry, texture and strong color changes can require more paint. Subtract doors and windows, include the ceiling only when it will be painted, and compare the result with the exact product label before buying.
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How the Paint Calculator works
This US paint calculator estimates gallons and whole containers for the walls of a rectangular room and an optional ceiling. It subtracts the square footage of doors and windows, then applies coats, editable coverage, container size and optional price.
Start with the surfaces, not the floor square footage
Wall area is room perimeter times ceiling height, less openings. The ceiling is length times width and is kept separate so it can be switched on only when it will actually be painted. The result also shows one-coat gallons, which makes product and color comparisons easier.
A quick floor-area multiplier misses ceiling height and openings. It can be useful for a rough quote, but a room model produces a more auditable purchase quantity without asking for every wall separately.
Coverage is an input, not a universal promise
The 400 ft² per gallon default is a planning value for one coat. Paint line, sheen, application method, texture, porosity and color change all move actual coverage. Replace the default with the range on the exact product label.
Bare drywall or masonry and strong dark-to-light changes may consume more or require primer. The calculator deliberately does not hide this uncertainty in an unexplained safety factor: coats and coverage remain visible and editable.
FAQ
How much paint does a 16 × 13 ft room need? expand_more
At 9 ft high, the walls total 522 ft². Subtract 54 ft² of doors and windows to get 468 ft². At 400 ft² per gallon and two coats, the estimate is 2.34 gallons for the walls.
Does the calculator include two coats? expand_more
The default is two coats, and the field is editable. Coverage is stated per coat, so changing from two to three coats increases the gallons by half.
Should I round gallons up? expand_more
Enter a container size sold for the selected paint. The calculator rounds the total job up to whole containers and shows the purchased volume and leftover paint, so it does not round every room independently.