Paint Calculator — How Much Paint for a Room or Wall

About this tool

Buying paint is a two-guess problem: guess too little and you are back at the store mid-wall, guess too much and the surplus dries out on a shelf. This calculator replaces the guessing with the same arithmetic a decorator uses — surface area, minus openings, times coats, divided by the paint's coverage — and then translates the result into actual cans to buy.

In room mode you enter length, width and ceiling height, and the wall area is computed as perimeter × height; in area mode you type the square meters directly, which suits a single wall, a ceiling (length × width) or a facade. Doors and windows are subtracted at standard sizes — 1.9 m² per door, 1.4 m² per window — and both the number of coats and the coverage are editable, with 11 m² per liter as a realistic default for wall paint on smooth plaster.

The answer comes in three forms: the net area you will actually paint, the liters required, and a suggested combination of standard can sizes (1, 2.5, 5 and 10 L) that covers the job with minimal leftover. A separate line restates the job in imperial terms — square feet and US gallons at the common 350 sq ft per gallon rule — for paint sold in gallon cans.

Coverage is the honest variable: it is printed on every can as a range, and rough, porous or unprimed surfaces land at the low end. Check your paint's own figure, prime fresh plaster, and plan around 10% reserve for touch-ups. Like every tool on this site, the calculator runs entirely in your browser — nothing you enter is uploaded or stored.

Example. A 12 square meter wall, no doors or windows, one coat, and coverage of 11 square meters per liter returns 1.1 liters.

Limit. Each door is subtracted as 1.9 square meters and each window as 1.4 square meters, and can sizes are only 10, 5, 2.5, and 1 liter.