1. Determine the length of your wall, or perimeter of the room, you plan to cover and round up to the nearest inch. Divide this number by 27 (27 inches is the width of a strip of wallpaper), which gives you the number of strips or “drops” of wallpaper you will need. Note: Normal sized windows and doors do not figure into the amount of wallpaper you need to cover a room. Do not subtract their area from the total wall area you are covering. Trust us.
2. Next, measure the height of the wall in inches, excluding baseboards and moldings. Add 4 inches to this number for leeway, then divide it by 36 (36 is the vertical repeat of most wallpapers), and round up to the nearest whole number. This is how many repeats per wallpaper strip you need. Multiply that number by 36, and you have the length in inches that each wallpaper strip should be. To determine the number in feet, divide it by 12.
3. Take this final number and multiply it by the number of strips you calculated in STEP 1. This should give you the total feet of wallpaper you need to cover your space. Divide this number by 30 (the number of feet in our wallpaper rolls) and round up to the nearest whole number. Voila! This is the number of wallpaper rolls you should order.
It is best to round up when ordering wallpaper rolls in the event that any paper is damaged during installation, or in case of future repairs.