Wallpaper Calculator

Buying wallpaper by guesswork almost always means buying too much. By calculating the number of rolls a room needs, accounting for pattern repeats and the openings left by doors and windows, you avoid paying for rolls you won't hang, and the leftover rolls you avoid buying also keep waste out of the landfill.

The math starts with total wall area, found by multiplying wall height by the combined width of the walls. The calculator then subtracts a standard 21 sq ft for each door and 15 sq ft for each window. It divides the remaining area by 25 sq ft, the usable coverage it assumes for a standard single roll after trimming, and rounds up. A pattern repeat cuts that coverage by the repeat length divided by 48 inches, capped at 25%, so any repeat of 12 inches or more leaves 18.75 sq ft per roll. Paste is estimated at one gallon for every four rolls at $25 a gallon, and the $45 price per roll is an editable default.

Round the result up to the next full roll every time. Coming up short partway through forces a fresh order, and a new batch can arrive in a slightly different shade. Busy patterns and long repeats eat more material than plain designs, so expect those to push the count higher. Tricky corners, alcoves, and odd cuts also draw down your supply faster than flat walls do.