Wallpaper Calculator — How Many Rolls Do I Need?
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Wallpaper is sold by the roll, and running out mid-wall with no matching batch left is the classic decorating disaster. This calculator works out how many rolls you need from your wall measurements, allowing for the pattern repeat — which is what most people forget, and what quietly adds a roll or two to bigger patterns.
Note: Rounds up to whole rolls and ignores doors and windows, which builds in a small safety margin. Always buy all rolls from the same batch number — different batches can differ subtly in colour.
How this calculator works
The calculator first works out how many vertical strips, or drops, are needed to go around the room: total wall length divided by the roll width. Then it finds how many drops it can cut from a single roll, dividing the roll length by the length each drop needs. That drop length is the wall height plus the pattern repeat, because with a patterned paper you must waste up to one full repeat on each drop to line the design up with its neighbour. Dividing drops needed by drops per roll, and rounding up, gives the number of rolls.
Worked example
A room with 20 metres of wall and 2.4 metre ceilings needs about 38 drops at the standard 0.53 metre roll width. With a plain paper, each 10.05 metre roll yields four whole drops, so you need 10 rolls. Add a 50 cm pattern repeat and each drop now consumes 2.9 metres instead of 2.4, dropping the yield to three whole drops per roll — so the same room needs 13 rolls. That is three extra rolls purely from the pattern, and the offcuts are why. Note that only whole drops count: a roll that yields 3.4 drops still gives you three usable ones.
Frequently asked questions
What is a pattern repeat?
The vertical distance before the design starts again. To make the pattern line up across adjoining strips, each drop must be cut at a matching point, wasting up to one full repeat per drop. It is printed on the roll label — a plain or textured paper has a repeat of zero, so enter 0.
What size is a standard roll of wallpaper?
The UK and European standard is 10.05 metres long by 53 cm wide, which is the default here. American rolls are commonly wider and shorter, often around 8.2 metres by 68 cm, so check your roll and adjust the fields.
Should I subtract doors and windows?
Generally no. Leaving them in creates a safety margin that covers cutting mistakes and pattern matching, which is where most shortfalls come from. Only subtract if the room has an unusually large opening such as patio doors or a wide bay.
Why does buying the same batch matter?
Wallpaper is printed in batches, and colours can shift subtly between them. Two rolls from different batches placed side by side can show a visible difference in daylight. Buy everything at once, and buy the spare roll up front rather than later.
How much extra should I buy?
One spare roll beyond the calculated figure is sensible on any job with a pattern. It covers mistakes during hanging and gives you matching stock for future repairs, which becomes impossible once the batch sells out.