All the walls added together, without deducting doors and windows.
Zero for a plain paper. A straight match repeats down the drop; an offset match wastes more.
How this calculation works
Why the repeat costs so much
Every drop has to start at the same point in the pattern, so on a repeat of sixty centimetres you lose up to sixty centimetres at the top of each drop. Over ten drops that is six metres — most of a roll. It is the single reason estimates for patterned paper come out short.
Why not deducting doors is the safe way round
The offcut above a door is rarely long enough to use anywhere else. Counting it as a full drop costs you a roll at most; not counting it costs you a second trip and possibly a second batch.
Frequently asked questions
Should I deduct doors and windows?
Not in this calculation. The offcuts above and below openings are mostly unusable, and the room where you would save a roll is the room where you least want to be short.
What is the difference between a straight and an offset match?
On a straight match the pattern repeats at the same height on every drop; on an offset match every second drop is shifted by half the repeat, which uses more.
How many spare rolls should I leave?
One, from the same batch, kept by the customer. A repair three years later is otherwise a whole wall.
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