Wallpaper bolt vs single roll — one bolt is two single rolls

What this diagram shows

A diagram explains the wallpaper ordering trap. Wallpaper ships as a bolt, which is a double roll, but it is still priced per single roll even though single rolls have not been packaged for decades, so a bolt equals two single rolls. Ordering six single rolls instead of six bolts gets you half the paper. The take-off is: strips equal the room perimeter divided by the roll width rounded up, bolts equal the strips divided by the strips per bolt rounded up, and single rolls equal bolts times two. For a 52-foot perimeter and a 20.5-inch-wide roll that is 31 strips, about 11 bolts before waste, or 22 single rolls. Every bolt should come from one dye lot so the color matches at the seams.