Wallpaper Calculator
Find out how many rolls of wallpaper you need, including extra for matching the pattern.
How to use this wallpaper calculator
Enter the room's length, width and wall height in feet, and count the doors. Then copy the roll size and the pattern repeat from the wallpaper label. The repeat is how far down the wall the pattern takes to line up again. Plain or random-match papers have a repeat of 0.
Instead of dividing square footage by roll size, the calculator counts strips: how many full-height strips fit on one roll, and how many strips go around the room. That's how paperhangers do it, because the leftover bit at the end of each roll is usually too short to use.
Common roll sizes
| Roll type | Width | Length | Area |
|---|---|---|---|
| US double roll | 20.5 in | 33 ft | about 56 sq ft |
| European roll | 20.5 in | 33 ft | about 56 sq ft |
| Wide or peel-and-stick roll | 27 in | 13 to 27 ft | check the label |
Many US wallpapers are priced per single roll but sold only in double rolls, so check whether the count on the label is single or double.
The math behind it
- Strip length = wall height + 4 inches for trimming + the pattern repeat.
- Strips per roll = roll length ÷ strip length, rounded down.
- Strips needed = (room perimeter − 3 ft per door) ÷ roll width, rounded up.
- Rolls = strips needed ÷ strips per roll, rounded up.
Example: a 12 × 10 ft room with 8 ft walls and one door has 41 ft of wall to cover. That's 24 strips of 20.5-inch paper. Each 100-inch strip means 3 strips per 33-foot roll, so you need 8 rolls.
Often used together
Quick answers
How many rolls of wallpaper do I need for a 12 × 12 room?
With 8 ft walls, one door and plain 20.5-inch paper on 33 ft rolls, about 9 rolls. A large pattern repeat can add one or two more.
Should I subtract windows?
This calculator doesn't, on purpose. The paper above and below windows still has to be cut from full strips, so subtracting them usually leaves you short.
How much extra wallpaper should I buy?
Keep at least one spare roll from the same batch for repairs. If you've never hung wallpaper before, one more for mistakes is a good idea.