Wallpaper Calculator
Find how many rolls of wallpaper a room needs, accounting for the drop length, roll dimensions and — crucially — the pattern repeat, which wastes more paper than most people expect.
How to use this calculator
- Enter the room's wall perimeter and height.
- Confirm your roll width and length (53 cm × 10.05 m is standard).
- Enter the pattern repeat from the roll label — this is what most estimates miss.
Formula used
With a pattern, each drop must be cut to a whole number of repeats so patterns align across seams — rounding the drop length up and wasting the difference. A larger repeat means longer effective drops and fewer usable drops per roll.
Example calculation
16 m perimeter, 2.5 m high, standard rolls, plain (no repeat): drop 2.5 m → 4 drops per roll, needing 31 drops → 8 rolls.
Add a 50 cm pattern repeat and each drop rounds up to 3.0 m → only 3 drops per roll → 11 rolls. The repeat alone added 3 rolls.
The pattern-repeat tax
Plain wallpaper wastes little, but patterned paper carries a hidden tax: for the design to line up across every seam, each vertical strip must start at the same point in the pattern, so strips are cut to whole multiples of the repeat and the leftover is discarded. A 2.5 m wall with a 50 cm repeat forces 3.0 m drops — 20% waste before you've hung a thing.
The larger the repeat, the worse it gets, and "offset" or "drop-match" patterns waste even more than straight-match ones. This is why patterned rooms routinely need 30–40% more paper than a naive area calculation suggests, and why the repeat figure on the roll label — not the room size — is the number that determines your order.
Why use this calculator?
- Factor in the pattern repeat that makes patterned rooms need far more paper.
- Work in drops and rolls the way decorators actually order.
- See exactly how much a pattern repeat costs you in extra rolls.
Frequently asked questions
How many rolls of wallpaper do I need?
Divide the wall perimeter by the roll width to get the number of drops, then divide the roll length by your drop height (rounded up to whole pattern repeats) to get drops per roll. A typical room takes 5–10 rolls; enter your figures for the exact number.
Why does the pattern repeat matter so much?
Patterns must align across seams, so each strip is cut to a whole number of repeats — wasting the leftover. A big repeat can turn a 2.5 m drop into a 3 m cut, meaning fewer usable strips per roll and more rolls overall.
What's a standard wallpaper roll size?
In Europe, 53 cm wide × 10.05 m long is the standard. American rolls differ. Always check your actual rolls, and buy them all from the same batch number so the colour matches.