The Calculator Helper

Wallpaper Calculator

Find how many rolls of wallpaper a room needs, allowing for the pattern.

m
m
m
m
m
Rolls needed
—
Drops needed
—
Usable drops per roll
—
Length per drop
—
With a spare roll
—

An estimate. Full drops are hung across doors and windows and trimmed, so openings are not subtracted.

From walls to rolls

Wallpaper is hung in vertical strips called drops. Divide the total wall run by the roll width to get the number of drops, then see how many drops each roll yields once the ceiling height and pattern repeat are accounted for.

drops = wall run ÷ roll width　·　rolls = drops ÷ drops per roll

A pattern repeat means each drop needs extra length to line up with its neighbour, which lowers how many usable drops you get from a roll. A plain paper wastes the least; a bold repeat the most.

Worked example

A room with 12 m of wall and a 2.4 m ceiling, papered with a standard 0.53 × 10.05 m roll, needs about 23 drops. With four usable drops per roll, that is 6 rolls — buy a spare in case.

Avoiding the mid-wall shortfall

Running out of a patterned paper part-way through a room is the worst time to discover batches differ. Estimating rolls up front, with a spare, keeps the job — and the colour match — consistent.

Practical tips

  • Mind the repeat. Larger repeats waste more; check the roll label before estimating.
  • One batch. Buy together and keep the batch number with any leftovers.
  • Hang past openings. Trimming around doors and windows is normal — don’t deduct them.

Frequently asked questions

What is a "drop"?
A drop is one full top-to-bottom strip of wallpaper. The number of drops is the wall run divided by the roll width; each roll yields a few drops depending on its length and the ceiling height.
How does the pattern repeat affect things?
A repeating pattern must line up between strips, so each drop needs a little extra length — up to one repeat. That waste means fewer usable drops per roll, so a large repeat can need noticeably more rolls.
Should I subtract doors and windows?
Usually not. You still hang full drops across openings and trim them, and the offcuts rarely make a clean extra drop, so leaving them in gives a safer estimate.
Why buy a spare roll?
Batches can vary slightly in colour, and mistakes happen. A spare from the same batch (note the batch number) saves a mismatched repair later.