Paint Calculator
How many gallons of paint a room needs, for the coats you plan.
What is Paint?
A paint estimate starts from wall area — the perimeter times the ceiling height — minus the doors and windows you will not paint (standard areas are subtracted automatically), times the number of coats, divided by the coverage printed on the can. The commonest wrong answer on the internet forgets the coats; the second commonest forgets that '350 sq ft per gallon' is one coat.
How it works
Wall area is computed as 2 × (length + width) × height, doors and windows are subtracted at 21 ft² and 15 ft² each (editable by entering your own counts), the total is multiplied by coats, and gallons are rounded up — part-cans do not exist and running short mid-wall shows as a colour shift between batches.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.