Wallpaper Roll Calculator
Count the wallpaper rolls for a room from its size, ceiling height, roll dimensions and pattern repeat.
How it works
perimeter = 2 × (length + width) · strips = ⌈perimeter in inches ÷ roll width⌉ · strip length = height + repeat · strips per roll = ⌊roll length ÷ strip length⌋ · rolls = ⌈strips ÷ strips per roll⌉
Wallpaper hangs in vertical strips (drops), each as wide as the roll, so the number of strips is the room perimeter divided by the roll width. Each strip must be at least the ceiling height, plus the pattern repeat because you trim the top of every strip to line the pattern up with the one beside it. Dividing the roll length by that strip length — rounded down — tells you how many good strips a roll gives, and the wasted tail is why patterned paper needs more rolls.
Worked example
A 12 × 10 ft room, 9 ft high, with a 20.5 in wide, 33 ft roll and no repeat: perimeter is 44 ft = 528 in, so 528 ÷ 20.5 = 26 strips. Each roll gives ⌊33 ÷ 9⌋ = 3 strips, so 26 ÷ 3 = 8.7, rounded to 9 rolls.
Frequently asked questions
Why does pattern repeat increase how much I need?
To match the design across a seam, you slide each new strip up or down by up to a full repeat and trim the excess. That trimmed piece is waste, so a large repeat can add a whole extra roll or two to the same room.
Do I subtract doors and windows?
This estimate counts full strips around the whole perimeter, which builds in a safety margin. You can subtract a strip for a large opening, but keeping the extra is wise — dye lots vary, so a mid-job top-up may not match.
Should I buy an extra roll?
Yes. Buy one spare from the same batch (dye lot) for miscuts and future repairs. Reordering later often means a different lot with a subtly different colour.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.