Wallpaper Pattern Repeat Calculator
Work out how many wallpaper rolls a patterned print really needs once you add the pattern-repeat waste from matching each drop.
How it works
Drop = ⌈height ÷ repeat⌉ × repeat · Strips = ⌈wall width ÷ roll width⌉ · Drops/roll = ⌊roll length ÷ drop⌋ · Rolls = ⌈strips ÷ drops-per-roll⌉
On a patterned wallpaper you cannot use every inch of the roll: each vertical strip must be cut so its print lines up with the strip beside it, which means rounding the cut length up to the next full pattern repeat and throwing away the offcut. The bigger the repeat, the more you waste per drop, and a roll only yields a whole number of usable drops. That is why a patterned room can need noticeably more rolls than the plain square-footage suggests.
Worked example
A 12 ft wide, 8 ft tall wall with 20.5" rolls 33 ft long and a 19" repeat: each drop rounds up to 6 × 19" = 9.5 ft, so a roll gives ⌊33 ÷ 9.5⌋ = 3 drops. You need ⌈144 ÷ 20.5⌉ = 8 drops, so 8 ÷ 3 rounds up to 3 rolls.
Frequently asked questions
What is a pattern repeat?
It is the vertical distance up the roll before the design starts over. To match neighboring strips you cut each drop to a whole number of repeats, so a 19-inch repeat means every drop is rounded up to the next 19-inch mark and the leftover is scrap.
Does a bigger repeat really cost more rolls?
Yes. A large repeat forces more length to be trimmed off every drop, so fewer usable drops come out of each roll. Plain or "random match" papers have effectively no repeat waste and go the furthest.
Should I buy an extra roll?
It is wise to add one roll for mistakes, future repairs and dye-lot matching — reordering later risks a different batch that does not quite match. This calculator gives the minimum; round your order up for safety.
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This calculator is for educational purposes. Double-check important results before acting on them.