First you need to determine how your wallpaper is sold, in double rolls or by the bolt. Double rolls tend to be produced in the US (in inches) and bolts (in centimeters) in the UK. You need to figure out the square footage of the walls you are going to apply the paper to. Then you need to calculate how many square feet are in each roll. Divide your wall square footage by the roll square footage and you will have the amount of rolls needed. You need to remember to account for a pattern repeat. If you have a large pattern, you will need more rolls. I know this is super confusing but don't worry our highly skilled wallpaper installer can calculate it for your job.