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Wallpaper Calculator: How Many Rolls Do I Need?
Work out how many rolls of wallpaper to buy for a room. The calculator counts full-height strips, allows for the pattern repeat and trimming, and subtracts doors and windows the way paperhangers do.
Why square footage alone gets wallpaper wrong
Dividing wall area by the area of a roll gives you a number that is almost always too low. Wallpaper goes up in full-height strips, and whatever is left on the roll after the last full strip is usually too short to use. Pattern matching makes this worse: each strip has to start at the same point in the design, so every strip uses extra paper.
The reliable method is to count strips:
- Strips around the room = perimeter in inches ÷ roll width, rounded up.
- Length of each strip = wall height + pattern repeat + about 4 in for trimming top and bottom.
- Strips per roll = roll length ÷ strip length, rounded down.
- Rolls = strips ÷ strips per roll, rounded up.
Doors and windows are handled by taking away whole strips only: a standard door (about 20 sq ft) and window (about 15 sq ft) are added up, and only the number of complete strips that area represents is removed. You still need short pieces above and below every opening.
Worked example
A 12 × 12 ft bedroom with 8 ft walls has a 48 ft perimeter. With a 20.5 in wide roll, that is 576 ÷ 20.5 = 28.1, so 29 strips. Each strip is 96 + 4 = 100 in, and a 33 ft (396 in) roll gives 3 strips. One door and two windows add up to 50 sq ft, which is 3 full strips, so you need 26 strips, or 9 rolls. The simple area method would have said 6.
Standard roll sizes
| Roll type | Typical size | Area |
|---|---|---|
| US double roll | 20.5 in × 33 ft | about 56 sq ft |
| US single roll (priced, sold in doubles) | 20.5 in × 16.5 ft | about 28 sq ft |
| Euro / metric roll | 21 in × 33 ft (0.53 × 10 m) | about 57 sq ft |
| Wide (peel and stick or commercial) | 27 in or 54 in × varies | check the label |
Many US papers are priced per single roll but packaged as double rolls. Enter the length of the roll you actually get.
Tips for buying wallpaper
- Check the dye lot. Rolls from different print runs can differ slightly in color. Buy enough at once, and note the batch number.
- Large repeats waste more. A 25 in repeat on 8 ft walls can drop you from 3 strips per roll to 2. Enter the repeat from the label.
- Drop match vs straight match. A drop (half-drop) match uses about the same paper as a straight match of the same repeat, but alternating strips start at different points, so cut from two rolls at a time.
- Accent wall only? Set the room width to 0 and the length to half the wall's width, so the perimeter equals the wall width.
Frequently asked questions
How many rolls of wallpaper do I need for a 12x12 room?
With 8 ft walls, a 12 × 12 ft room needs about 26 strips of 20.5 in paper after one door and two windows. A 33 ft double roll gives 3 strips, so buy 9 double rolls.
How much does a double roll of wallpaper cover?
A standard US double roll is 20.5 in × 33 ft, about 56 sq ft. After trimming and pattern matching, plan on using only 40 to 45 sq ft of it.
Does pattern repeat affect how much wallpaper I need?
Yes. Each strip must be cut longer by up to one full repeat so the pattern lines up. A large repeat can drop the number of strips per roll from 3 to 2, which means up to 50% more rolls.