Wallpaper Rolls Calculator NZ
This calculator works out how many rolls of wallpaper you need to paper a room in New Zealand, taking account of the roll size and the pattern repeat that quietly increases how much you use. Wallpaper is sold by the roll, and because each roll only yields a certain number of full-height strips, or drops, the number of rolls is rarely as simple as dividing the wall area, especially with a patterned paper where length is lost at the top of each drop to line the pattern up. Get it wrong and you either run short, with the risk of a mismatched batch, or are left with costly spare rolls. The method is to divide the wall perimeter by the roll width to find how many drops you need to go around the room, then work out how many drops you get from one roll given the wall height plus the pattern repeat, and divide one by the other. You enter the wall perimeter, the wall height, the roll length and width, and the pattern repeat, and the calculator returns the number of rolls needed and the drops required. Use the full perimeter for a safe estimate, buy all rolls from the same batch for a consistent pattern, and keep any offcuts for repairs. An estimate to plan and budget your wallpapering.
Uses the full perimeter for a safe estimate. A larger pattern repeat means fewer drops per roll. Buy from one batch. An estimate for planning only.
How it works
The number of drops is the wall perimeter divided by the roll width, rounded up. The drops per roll is the roll length divided by the wall height plus the pattern repeat, rounded down to whole drops. The rolls needed is the drops divided by the drops per roll, rounded up.
Worked example
A room with a 16 metre perimeter and 2.4 metre walls needs 31 drops using 0.53 metre wide rolls. A 10 metre roll yields 4 drops of 2.5 metres each (2.4 plus a 0.1 metre repeat), so 31 drops needs 8 rolls.
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