Orpheus

How Many Rolls of Wallpaper?

Counted in drops, with the pattern repeat included.

Inputs
m

Add up all four walls. Do not subtract doors and windows yet.

m
cm

On the roll label. Zero for a plain or random-match paper.

m
cm

Each saves roughly one drop.

Rolls to buy
9
Drops needed
27
Usable drops per roll
3
Length cut per drop
2.56 m
Wasted per drop by the repeat
16 cm
Wall area
36 m²
Cost
270.00
drops = perimeter ÷ roll width · rolls = drops ÷ drops per roll

The 32 cm repeat forces each drop to 2.56 m, wasting 16 cm every time. A larger repeat can add a whole roll to the same room — which is why area alone never answers this question.

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Divide the perimeter by the roll width for the number of drops, round each drop up to a whole pattern repeat, then see how many fit in a roll. Area alone gives the wrong answer.

How to use Wallpaper Calculator

  1. Measure the perimeter and height. All four walls added together, floor to ceiling.
  2. Enter the pattern repeat. From the roll label — zero for plain paper.
  3. Read the roll count. Based on usable drops per roll, not on square metres.

About calculating how many rolls of wallpaper are needed

Wallpaper is the one decorating material where calculating by area gives a confidently wrong answer. The paper is hung in full-height drops, and the offcut at the end of a roll is almost never long enough to become another drop, so a roll never covers its nominal area on a real wall. The correct unit is the drop: divide the room perimeter by the roll width to find how many are needed, work out how many complete drops fit into a roll, and divide. The pattern repeat is what turns this from arithmetic into a real constraint. Adjacent drops must line up, which means every drop begins at the same point in the design and is therefore cut to a whole number of repeats rather than to the wall height. A twenty-centimetre repeat on a two-metre-forty wall costs almost nothing; a sixty-four-centimetre repeat forces a two-metre-fifty-six cut and throws away sixteen centimetres on every single drop. Across fifteen metres of perimeter that is frequently an entire extra roll for exactly the same room, which is why two papers with identical coverage figures can need different quantities. Openings should be counted conservatively. Subtracting the true area of a door or window over-estimates the saving badly, because the wall above and below still needs covering and usually still takes a full-length cut. One drop per opening is the conventional allowance. As with flooring and paint, buy the whole job in one batch and keep a spare roll — print runs differ enough to be visible, and a later top-up rarely matches.

Frequently asked questions

Why not just divide the wall area by the roll area?
Because wallpaper is hung in full-height strips and the leftover at the end of a roll is usually too short to be another drop. A roll covering 5 m² does not cover 5 m² of wall — it covers however many complete drops fit into its length, which is always fewer.
What is a pattern repeat and why does it matter so much?
The distance before the design starts again. Every drop has to begin at the same point in the pattern to line up with its neighbour, so each is cut to a whole number of repeats. A 64 cm repeat on a 2.4 m wall forces a 2.56 m cut — 16 cm wasted on every drop, which across a room is often a whole roll.
Should I subtract doors and windows?
Roughly one drop each, and no more than that. The wall above and below a window still needs papering and still consumes a full-length cut in most cases, so subtracting the actual area badly under-orders.
What is a straight match versus an offset match?
A straight match repeats at the same height on the next drop. An offset or drop match staggers it by half a repeat, which uses the offcuts better and slightly reduces waste — but the calculation above assumes the less favourable straight match, which is the safer direction to be wrong in.
Should I buy a spare roll?
Yes, and check the batch number matches. Colour varies between print runs enough to show on a wall, so an extra roll bought later rarely matches. One spare is cheap insurance against a torn drop or a damaged patch years afterwards.

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