Wallpaper calculator: how many rolls do you need
Add up the length of every wall you want to cover and enter it as the room perimeter, then enter the wall height. Type the roll width, the roll length and, if your paper has a pattern, the repeat, all read on the label.
The calculator returns the number of strips to hang, how many strips one roll gives, and the number of rolls to buy.
Enter your measurements, then calculate.
Method and limitations
Strips needed = perimeter ÷ roll width, rounded up. Strips per roll = roll length ÷ (wall height + pattern repeat), rounded down, because a strip cannot be joined from leftovers. Rolls = strips needed ÷ strips per roll, rounded up. Imperial: perimeter, height and roll length in feet, roll width and pattern repeat in inches, with 1 ft = 12 in exactly. Metric: perimeter, height and roll length in meters, roll width and pattern repeat in centimeters. The roll width, roll length and pattern repeat depend on the paper, so none is assumed: type the ones printed on the label. If a strip is longer than the roll, no whole strip fits and the calculator reports an error. Doors, windows, trimming allowance and the extra needed for a particular wall are not computed: reduce the perimeter or add a roll yourself. This is a geometric calculation, so no external source is needed.
Sources
No external reference is documented for this calculation; its method and limitations are described above.
