(See also How many rolls of log wallpaper will I need?)
Border: Borders are 15 feet long, unless otherwise noted. In order to allow for pattern matching, you will need 1 to 2 extra feet for each roll after the first roll. For example, if you have 60 feet of wall length to cover with border, 60 divided by 15 is 4. Then add 1 to 2 feet each, depending on the pattern repeat, for rolls 2,3 and 4. That would be an extra 3 to 6 feet, in addition to the 60 feet. So you would need 5 rolls for this project.
Double rolls of wallpaper contain approximately 56 sq.ft. With a few exceptions, they are 33 feet long and 20.5 inches wide. Begin by figuring how many square feet of wall area you plan to cover. A wall 10 feet long and 8 feet high is: 8 x 10 = 80 square feet. A 12 foot by 14 foot room with an 8 foot high ceiling would be: two 12 foot walls and two 14 foot walls = 52 feet around the room, times 8 feet high = 416 square feet.
Next, deduct for any doors, windows or other openings. As a rule of thumb, for an average door deduct 18 square feet, and 15 square feet for an average window. For other openings, measure the width and height and multiply to get square measurement.
If you multiply inches by inches, you will get square inches. That will work too. Then divide by 144 to get square feet. For example, an opening 30 inches wide by 80 inches high would be: 30 x 80 = 2400 square inches divided by 144 = 16.6 square feet.
After subtracting openings, you should have the net square feet of wall area you want to cover. If the pattern repeat is less than 12 inches, divide by 46 to get the number of DOUBLE rolls you will need. If the pattern repeat is 12-16 inches, divide by 40. If the pattern repeat is more than 16 inches, divide by 38.
For example: A 12 by 14 foot room, with 8 foot ceilings has 416 square feet. If we deduct for 1 average door and 1 average window, 416 - 18 - 15 = 383 net square feet. If the pattern match is 10 inches, divide 383 by 46 = 8.3 DOUBLE rolls. Round this number up to 9. You need to order 9 DOUBLE rolls.
When in doubt, it is usually better to order too much wallpaper than too little. Extra double rolls can be returned for a refund. But if you need to order more, it may not be possible to get the same dye lot or run number. That means the colors could be different. Or the pattern may even be discontinued.
For our customers outside the US: Please note that a standard European roll of wallpaper is equivalent to what we call a DOUBLE roll.