Most of our Traditional Wallpaper is sold by the "double roll" and is one long roll that's 27 feet long and 24 inches wide (there are a few exceptions to this, so please refer to the item's description details). If you would like to calculate how many rolls you need, consider the height and width of your room, pattern repeat (found under the Description tab on the product page), and whether it is a straight or step match (found under the Description tab on the product page).  Our Peel & Stick Wallpaper is sold by the sheet and there are 3 size options (width x length): 24” x 48”, 24” x 96”, and 24” x 144”. Select the height you will need for your ceilings. From there, you need to know how many sheets you'll need for your wall width. There will be a 1/4" overlap at the seams. Unlike Traditional Wallpaper, you do not need to account for the pattern repeat - if you order based on your ceiling height, the patterns will line up side by side with a 1/4" overla