How it works
Enter the room size and the roll details from the label. The calculator figures how many full-height strips you can cut from each roll (after allowing for the pattern repeat), converts that to usable square feet, and divides the net wall area by it.
Counting only full strips builds in realistic waste: the leftover piece at the end of every roll is usually too short to use. A larger pattern repeat means more paper lost matching each strip to the one beside it.
Wallpaper in the US is usually sold in double rolls about 20.5 inches wide and 33 feet long (about 56 sq ft). Buy all rolls from the same batch or dye lot and keep one spare.
Formula
Strips per roll = ⌊roll length ÷ (wall height + repeat)⌋. Usable area per roll = strips × roll width × wall height. Rolls = net wall area ÷ usable area, rounded up.
Questions people ask
What is a double roll of wallpaper?
Most US wallpaper is priced per single roll but sold in double rolls, which are one continuous roll twice as long, typically 20.5 in by 33 ft (about 56 sq ft). A double roll gives more full strips with less waste.
How does pattern repeat affect how much I need?
Each strip must be cut long enough to line the pattern up with its neighbor. With a 21 inch repeat on 8 ft walls, a 33 ft roll yields 3 strips instead of 4.
Should I subtract doors and windows?
Subtracting them is reasonable for standard doors and windows. For a single small window, many installers skip the deduction because offcuts above and below it are hard to use.