Wallpaper Calculator
This calculator works out how many rolls of wallpaper you need to buy for a room, so you order enough without paying for rolls you will never use. You enter the perimeter of the room in metres, the wall height, the length and width of a single roll, and a waste percentage to allow for trimming and matching the pattern. From these figures it works out the total wall area, how much usable coverage one roll gives once waste is deducted, and the number of rolls to buy, rounded up to a whole number. Because the perimeter measurement ignores doors and windows, the wall area is slightly overstated, which builds in a small safety margin rather than leaving you short partway through the job. The waste allowance matters more than people expect: a plain paper might only need 10% for trimming, while a large pattern repeat can need 20% or more, because each strip has to line up with the last and that wastes more of every roll. As a guide, a standard 10 by 0.53 metre roll covers about 5 square metres before waste is taken off. Always round your final figure up to a full roll and buy at least one spare from the same dye batch, since colour can vary slightly between batches and running short midway through hanging costs far more than one leftover roll.
Excludes doors and windows, which gives a small safety margin. Increase waste for large pattern repeats.
How it works
The wall area is the perimeter times the height. One roll covers its length times its width, less the waste from trimming and matching the pattern. Divide the wall area by the usable roll coverage and round up to whole rolls.
Worked example
A room 16 metres around and 2.4 metres high has 38.4 square metres of wall. A 10 by 0.53 metre roll is 5.3 square metres, but with 15% waste it usefully covers about 4.5 square metres, so you need about 9 rolls.
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