Wallpaper Roll Calculator
Square footage is the wrong way to order wallpaper: paper is used in whole strips, and a large pattern repeat can waste half a roll. This counts drops wall by wall, the way installers and the paper makers do, then turns them into rolls.
How this calculator works
- Drops per wall: each wall's width divided by the roll width, rounded up to whole strips.
- Cut length: the wall height plus the trim allowance, rounded up to a whole number of pattern repeats, because every strip has to start at the same point in the pattern. With no repeat it is simply the height plus trim.
- Half drop: every other strip starts half a repeat further down the pattern. Following Thatcher's estimate of one extra half repeat of material per double roll, half a repeat is set aside on every roll.
- Drops per roll: the roll length divided by the cut length, rounded down. What is left at the end of each roll is offcut.
- Rolls: total drops divided by drops per roll, rounded up.
Doors and windows are not deducted. Makers disagree on whether to, and the offcut above a door and below a window is roughly the material a full-height strip wastes. Farrow & Ball advise adding one more roll whatever you estimate, and because rolls from different print runs do not match exactly, that spare should come from the same run number as the rest. Check the run numbers on every roll before anything is cut.
Every figure here comes from our guide, How Much Wallpaper to Buy: Roll Size, Pattern Repeat, and Waste, which explains each rule and the exceptions in full.
Sources
- Sanderson: FAQs (drops per wall, drop length, roll size 52 cm x 10.05 m)
- Farrow & Ball: calculating wallpaper quantities (drops per roll, one extra roll)
- York Wallcoverings: roll sizes and run numbers
- Cole & Son: frequently asked questions (match types, batch numbers)
- Wallcovering Installers Association: wallcovering dictionary (pattern repeat)
- Thatcher: pattern repeats and pattern matches (half drop allowance)