Should I round up further?

The result already rounds every stage up. One spare roll is still worth having for later repairs, since batches go out of stock long before the paper wears out.

Why is my roll 53 cm wide?

It is the European standard width, paired with a 10.05 m length. American rolls are commonly 68.6 cm and shorter, so change both fields if your paper is not metric.

Wallpaper Calculator — How Many Rolls Do I Need?

A patterned paper wastes some of every drop, because each one has to start at the same point in the design.

Room length (m)5.0

Room width (m)4.0

Ceiling height (m)2.50

Pattern repeat (cm)0

Number of doors1

Number of windows1

Fine tuning

Roll length (m)

Roll width (cm)

Rolls to buy

Drops needed

Drops per roll

45.0 m²

Wall area

The pattern repeat, not the wall, decides how many rolls you buy

Wall area gets you a rough roll count and then betrays you. What really drives the number is the repeat: every drop has to start at the same point in the design, so each one is cut to the next whole repeat above your wall height. A 64 cm repeat on a 2.5 m wall wastes 34 cm on every single drop.

How it works

Counts the drops needed around the room from the perimeter and the roll width.
Rounds each drop up to a whole number of pattern repeats, which is where the waste appears.
Works out how many whole drops come out of one roll, and therefore how many rolls to buy.

perimeter    = 2 × (length + width)
drops        = ceil(perimeter / roll width) − allowance for doors and windows
drop length  = ceil(wall height / repeat) × repeat     (plain paper: wall height)
drops/roll   = floor(roll length / drop length)
rolls        = ceil(drops / drops per roll)

Worked example

A 5 × 4 m room, 2.5 m high, standard 10.05 m × 53 cm rolls, one door and one window.

perimeter = 2 × 9 = 18 m → ceil(18 / 0.53) = 34 drops, less 1 for the openings = 33
plain paper: drop = 2.5 m, so floor(10.05 / 2.5) = 4 drops per roll → ceil(33 / 4) = 9 rolls
with a 32 cm repeat: drop = ceil(2.5 / 0.32) × 0.32 = 2.56 m
floor(10.05 / 2.56) = 3 drops per roll → ceil(33 / 3) = 11 rolls

The same room, the same paper size: 9 rolls plain, 11 rolls patterned. The repeat costs two rolls, and no wall-area calculation would have told you.

Reading the result

Doors and windows are counted as roughly half a drop each. That is deliberately conservative — offcuts above a door are rarely long enough to reuse, and running short mid-wall is far worse than one spare roll.
Buy every roll in one batch and check the batch number. Colour varies between print runs enough to see on a joined wall, and a matching roll bought a month later often is not one.
A free-match paper has no repeat at all: enter 0 and the calculation reverts to plain drops.

Common questions

Should I round up further?: The result already rounds every stage up. One spare roll is still worth having for later repairs, since batches go out of stock long before the paper wears out.
Why is my roll 53 cm wide?: It is the European standard width, paired with a 10.05 m length. American rolls are commonly 68.6 cm and shorter, so change both fields if your paper is not metric.