How the wallpaper calculator works
Wallpaper goes up in vertical strips, so it's counted by strips, not square feet. Each strip is the wall height plus 4 inches for trimming plus the pattern repeat.
Strips needed = (room perimeter − door widths) ÷ roll width
Strips per roll = roll length ÷ strip length, rounded down
Example: a 12 × 10 ft room with 8 ft walls
The perimeter is 44 feet. Minus one 3 ft door leaves 41 feet, or 492 inches, which takes 24 strips of 20.5 inch paper. Each strip is 100 inches, and a 33 ft roll gives 3 strips, so buy 8 rolls, about $360 at $45 each.
Windows aren't subtracted, because you still need strips above and below them. Buy all rolls from the same batch number.
Frequently asked questions
How does pattern repeat affect wallpaper?
A larger repeat means more paper is lost lining up the pattern, so each roll yields fewer strips. Enter the repeat from the label.
How many square feet are in a roll of wallpaper?
A standard US double roll (20.5 in × 33 ft) holds about 56 square feet, but you'll use less than that once trimming and matching are allowed for.
Last reviewed: 2026-10-31