Wallpaper Calculator
Free wallpaper calculator. Estimate how many wallpaper rolls you need by room size and pattern repeat. No signup.
A wallpaper calculator estimates how many rolls paper a room by counting full-height strips instead of dividing wall area by roll area, because pattern matching means a roll’s usable length is shorter than its label.
Why strip counting beats area division
Wallpaper cannot be used edge to edge with zero waste. Every strip has to align with the one beside it, and each drop needs a little extra at the top and bottom for trimming. The calculator therefore works out how many strips the room needs, how many strips each roll yields, and divides one by the other:
perimeter = 2 × (length + width), andwall area = perimeter × heightdrop length = height + 0.5 ft, the 6-inch trimming allowance- With a pattern repeat r inches:
drop length = ceil((drop × 12 + r) ÷ r) × r ÷ 12 strips needed = ceil(perimeter ÷ (roll width ÷ 12))strips per roll = floor(roll length ÷ drop length), thenrolls = ceil(strips needed ÷ strips per roll)
The pattern-repeat line rounds the drop up to the next whole repeat, which is exactly why a large repeat raises the roll count. There is no doors or windows field, so the tool treats the walls as continuous; for a room with several large openings, buy accordingly or measure those walls separately.
Worked example: a 12 × 10 ft room, 8 ft walls
Defaults: length 12 ft, width 10 ft, height 8 ft, roll width 21 in, roll length 33 ft, no pattern repeat.
| Step | Calculation | Result |
|---|---|---|
| Perimeter | 2 × (12 + 10) | 44 ft |
| Wall area | 44 × 8 | 352 ft² |
| Drop length | 8 + 0.5 | 8.5 ft |
| Strips needed | 44 ÷ 1.75 = 25.14, round up | 26 strips |
| Strips per roll | 33 ÷ 8.5 = 3.88, round down | 3 strips |
| Rolls | 26 ÷ 3 = 8.67, round up | 9 rolls |
A roll of 21 in × 33 ft covers 57.75 ft² on the label, but only about 52 ft² of actual wall after the trimming allowance. Buying 9 single rolls is 4.5 double rolls, so plan on 5 double rolls if that is how your wallpaper is sold.
Reference: strips per 33-foot roll
| Wall height | Drop length | Strips per roll | Linear wall per roll |
|---|---|---|---|
| 8 ft | 8.5 ft | 3 | 5.25 ft |
| 9 ft | 9.5 ft | 3 | 5.25 ft |
| 10 ft | 10.5 ft | 3 | 5.25 ft |
| 11 ft | 11.5 ft | 2 | 3.50 ft |
| 12 ft | 12.5 ft | 2 | 3.50 ft |
Notice how the strips per roll holds at 3 until the drop passes 11 feet, then drops to 2. A tall room loses a whole strip per roll, which is a large jump in cost. Pattern repeats push the drop length up and can trigger the same drop from 3 strips to 2.
Common mistakes
- Dividing wall area by roll area. That ignores trimming and matching, and it always underestimates. Strip counting is the accurate method.
- Ignoring the pattern repeat. Enter it when the wallpaper has one; a 20-inch repeat can cut a 33-foot roll from 3 strips to 2.
- Confusing single and double rolls. Many patterns are priced per double roll but list coverage per single. Check the label before ordering.
- Buying exactly the count. Keep one spare roll for future repairs; dye lots vary and a later match may not exist.
How many rolls of wallpaper for a 12 × 10 room?
Nine single rolls at 8-foot ceilings with 21 × 33-foot rolls and no pattern, which is 4.5 double rolls. A pattern repeat can push this higher.
Does a pattern repeat change the roll count?
Yes, because each drop must round up to a whole repeat. A repeat large enough to push the drop past 11 feet drops a roll from three strips to two, raising the count sharply.
Should I subtract doors and windows?
This calculator does not. Small openings are usually papered around with offcuts, so subtracting them can leave you short. For a wall that is mostly glass or a large sliding door, measure that wall separately.
Wallpaper and paint are alternatives for the same walls, so the paint calculator is a useful comparison. If you are redoing the wall surface first, the drywall calculator prices the new sheets.