Wallpaper is printed in two standard widths, 21 inches and 27 inches. These sizes compose an industry standard, with 21-inch wallpaper being 16.5 feet long and 27-inch wallpaper being 13.5 feet long.
Be aware that all manufacturers of wallpaper package their products in multiples of two. This means that every package of wallpaper actually contains two sheets of paper.
Wallpaper first gained popularity as a home decoration during the Renaissance as a variation on the hanging tapestries that had been popular for centuries. That first wallpaper was printed with woodblocks, but of course, now, the patterns on most sheets of wallpaper are printed by machine.