How it works
The strip method
Wallpaper hangs in vertical strips, and a strip cannot be pieced across the end of a roll. So counting whole strips is more accurate than dividing wall area by roll area, which always comes out low. We do both and order from the strips.
strips per roll = roll length ÷ strip length, rounded down
strips needed = wall width ÷ roll width, rounded up, less the whole strips each door spans
double rolls = strips needed ÷ strips per roll, rounded up
Assumptions
- Roll size: 20.5 in × 33 ft, a standard US double roll. Edit both fields if your label says otherwise.
- Trim: 4 in per strip, 2 in at the top and 2 in at the bottom, so you can cut the paper square. This is a rule of thumb. Installers often allow 2 to 4 in per end.
- Pattern repeat: one full repeat is added to every strip so the pattern can match from strip to strip. This is the cautious method; a skilled installer sometimes saves a little.
- Doors: each door saves only the whole strips that fit across its 3 ft width (1 strip of a standard 20.5 in roll), because the paper above the door still comes from a full-length strip. We never order fewer rolls than the plain wall area needs. Windows save none, for the same reason. This is a rule of thumb, kept low on purpose. The area cross-check takes off 20 sq ft per door and 15 sq ft per window.
- We never go below 1 strip. A strip longer than the roll gives no answer, because the roll cannot cover that wall.
- Metric: type meters and centimeters. Sizes are converted for the math, and prices stay per double roll.
Worked example
A 12 × 12 ft room, 8 ft walls, 1 door, 1 window, no pattern repeat
- Wall to cover: 2 × (12 + 12) = 48 ft = 576 in
- Strips across: 576 ÷ 20.5 = 28.10, rounded up to 29. Take off 1 for the door: 28 strips
- Strip length: 96 + 0 + 4 = 100 in
- Strips per roll: 396 ÷ 100 = 3.96, rounded down to 3
- Rolls: 28 ÷ 3 = 9.33, so buy 10 double rolls
- At $70 a double roll (the middle of our typical range): $700
- Cross-check by area: 349 sq ft ÷ 56.4 = 6.19, which rounds to 7 rolls. Too low, because the end of each roll is wasted.
Common room sizes, double rolls
| Room | Strips | No repeat | 21 in repeat | Area only |
|---|---|---|---|---|
| 10 × 10 ft | 23 | 8 | 8 | 6 |
| 12 × 12 ft | 28 | 10 | 10 | 7 |
| 12 × 14 ft | 30 | 10 | 10 | 7 |
8 ft walls, 1 door and 1 window, 20.5 in × 33 ft rolls. "Area only" is the simple wall area ÷ roll area cross-check, which runs low. A repeat makes no difference on 8 ft walls here because 3 strips still fit on a roll.
Questions people ask
How many rolls of wallpaper for a 12x12 room?
With 8 ft walls, 1 door and 1 window and no pattern repeat you need 28 strips, 3 per roll, so 10 double rolls. Simple area math says 7, which would leave you short.
What is a pattern repeat?
It is the vertical distance before the design starts over. Strips must line up, so each one has to be cut with extra length to match. A bigger repeat wastes more paper. On 9 ft walls, the same room needs 10 double rolls with no repeat but 14 with a 21 in repeat, because only 2 strips fit on a roll instead of 3.
What is the difference between a single and a double roll?
A double roll is twice as long as a single. A US double roll covers about 56 sq ft, and a single about 28 sq ft, but stores often print the price per single roll. Our price is per double roll, so if your label shows a single-roll price, double it, or enter your price for the roll size you set above.
How much extra should I order?
The strip count already includes trim and pattern waste. Buy every roll from the same batch, because dye lots can differ in color. Order all of them at once, and keep one spare roll for repairs if the pattern is a custom or discontinued one. One extra double roll in this room adds about $70 at typical prices.
How many rolls for an accent wall?
Switch to "Single wall" and enter its width. A 12 ft wall with 8 ft height and no openings needs 8 strips, 3 per roll, so 3 double rolls. Hanging one wall still means whole strips, so you will have leftover paper.