try a color on the walls
Walls: Terracotta example colors, not products
This room: 12 × 12 ft, 8 ft walls, one door and two windows · 2 coats · 350 sq ft per gallon on the can
2 gallons + 1 quart337 sq ft × 2 coats + 10% ÷ 350 = 2.12 gal, rounded up to cans
Calculate your roomMeasure the room, read the label, buy the right number of cans, rolls and boxes.
Three calculators for interior paint, wallpaper and flooring. Each one shows its arithmetic and rounds up to the packages you can actually buy.
Guides
Worked examples and label-reading notes, checked against manufacturer pages.
- Primer is a separate can: how much one coat takes2026-10-13 · Paint calculator
- Benjamin Moore paint calculator: four products, two numbers2026-10-06 · Paint calculator
- Wall square feet to paint cans: the whole table, and where it steps2026-10-03 · Paint calculator
- Paint calculator per square foot: which number goes in, and what a square foot takes2026-10-02 · Paint calculator
- The wallpaper calculator refused my half-drop. Here is why I let it2026-10-01 · Wallpaper calculator
How these calculators work
Every answer starts with two things you supply: a measurement you took, and the number printed on the product you intend to buy. The calculators never quietly substitute a default for the figure on your own can, roll or carton, because that figure is what moves the answer.
Paint takes the wall area, subtracts only the openings you measured, multiplies by the number of coats, divides by the coverage printed on the label, adds the allowance you choose, and rounds up to the can sizes you said you can buy. Wallpaper counts full-height strips, cuts each strip at the next pattern repeat, reserves one repeat at the start of every roll, then turns strips into physical rolls and physical rolls into the packs a seller actually sells. Flooring adds your allowance to the measured area, divides by the square feet printed on the carton, and rounds up to whole cartons. Each result shows the arithmetic that produced it, so you can check it against your own page of notes.
What they do not do
They do not price anything, rank products or recommend a brand, and they do not replace the instructions on the package. They do not reuse offcuts, pool short pieces at a corner, or plan stairs, transitions, primer or trim, and a ceiling is included only if you measure it separately. Half-drop and offset wallpaper matches, murals and panel sets are refused rather than estimated, because those need a cutting plan from the manufacturer rather than a strip count.
Where the numbers in the guides come from
Product figures quoted in the guides are read from the manufacturer's own page or technical data sheet, quoted as printed, and recorded with the date they were read. The worked examples are recomputed with this site's own calculation code before publication, and a review date is never renewed just because a scheduled check ran. When a manufacturer does not publish a figure, the guide says so instead of estimating one.