Wallpaper Repeat Calculator

Wallpaper is sold and cut in vertical strips, so this calculator works the way a paperhanger actually plans a job rather than just dividing total square footage by roll size. It first finds how many strips will fit around your room by dividing the room's perimeter (in inches) by the roll's width. Then it determines how long each strip must be cut: if your paper has a pattern repeat, each strip is rounded up to the next full multiple of that repeat distance above your ceiling height, because patterns must align at the seams between strips — a non-repeating or solid pattern simply uses the ceiling height directly. A flat 4-inch trim allowance is added to every strip for top and bottom trimming.

From there, it calculates how many full strips fit in one roll's length and divides your total strip count by that to get the number of rolls to buy, always rounding up. The larger your pattern repeat relative to your ceiling height, the more each strip gets rounded up and the more cut-off waste accumulates — that's why the calculator also reports a waste percentage, comparing the total wallpaper you'll purchase against the room's actual wall area. A pattern repeat of 0 minimizes waste since strips need no repeat-matching, while large repeats (18-24"+) common in bold traditional prints can push waste well above 20%. Always round up rather than down when buying, since dye lots between separately purchased rolls can vary and running short mid-job risks a visible mismatch.