A 12 × 14 ft room with 8 ft walls takes 31 strips of 20.5 in wallpaper to go all the way round. With a 21 in pattern repeat each strip needs 9 ft 9 in of paper, so a 33 ft double roll gives three strips — 11 rolls, or 13 with 10 % reserve. Counting by square feet would have said 8. The calculator above counts strips for a rectangular room or any shape you draw on the plan.
How the calculator works
For a rectangular room, enter the length, width and wall height. For an L-shaped room, a bay or a hallway, switch to Any shape and drag the corners on the plan, click + on a wall to add a corner, or type each wall's length. Add windows and doors to the walls they sit on — you can slide them along the wall — then choose the roll, the pattern repeat and the reserve.
Why strips, not square feet
Wallpaper goes up in full-height strips that must line up with the pattern. Every strip is the wall height plus up to one repeat; whatever is left at the end of a roll, shorter than a strip, is waste. That leftover is why dividing the wall area by the roll area always comes out short.
The count
- Strips around the room = perimeter ÷ roll width, rounded up: 52 ft ÷ 20.5 in = 31.
- Strip length = wall height + repeat: 8 ft + 21 in = 9 ft 9 in.
- Strips per roll = roll length ÷ strip, rounded down: 33 ÷ 9.75 = 3.
- Rolls = strips ÷ strips per roll, rounded up, plus the reserve: 31 ÷ 3 = 11, with 10 % 13.
| Repeat | Strip on 8 ft walls | Strips per 33 ft roll | Rolls for 31 strips |
|---|---|---|---|
| 0 (random) | 8 ft | 4 | 8 |
| 12 in | 9 ft | 3 | 11 |
| 21 in | 9 ft 9 in | 3 | 11 |
| 25 in | 10 ft 1 in | 3 | 11 |
Windows and doors
The pieces above and below a window and above a door are cut from full strips, so openings do not reduce the strip count. The calculator still shows the area to paper — for adhesive, primer or sizing.
Rolls in the US
Most wallpaper sold in the US comes in double rolls about 20.5 in × 33 ft (56 ft²), often priced per single roll. Wide papers come 27 in × 27 ft. Buy every roll with the same batch or lot number: two batches can differ in shade.
Common mistakes
- Dividing area by area. It ignores the waste at the end of every roll.
- Forgetting the repeat. A large repeat can cost one strip in four.
- Buying exactly enough. Keep a spare roll for repairs: the same batch is rarely available later.
For paint instead of paper, use the Paint Calculator.