How this calculator works
Wallpaper is hung in full-height strips, so this calculator counts strips around the room, works out how many strips fit in one roll (after pattern repeat and trimming), and divides. Doors and windows are not deducted because their offcuts rarely save a full strip.
Strips = round up( Perimeter (in) ÷ Roll width )
Strip length = Wall height (in) + Pattern repeat + 4 in trim
Strips per roll = floor( Roll length (in) ÷ Strip length )
Rolls = round up( Strips ÷ Strips per roll )
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Room length | 12 ft |
| Room width | 10 ft |
| Wall height | 8 ft |
| Roll width | 20.5 in |
| Roll length | 33 ft |
| Pattern repeat | 0 in |
| Width of openings to skip | 0 ft |
| Result | Value |
|---|---|
| Rolls needed | 9 rolls |
| Strips needed | 26 strips |
| Strips per roll | 3 |
| Cut length per strip | 100 in |
Step by step:
- Perimeter to cover = 44 ft = 528 in
- Strips = 528 ÷ 20.5 → 26
- Each strip = 96 + 0 repeat + 4 trim = 100 in
- Strips per roll = floor(396 ÷ 100) = 3; rolls = 26 ÷ 3 → 9
Double rolls needed by room size
8 ft walls, 20.5 in × 33 ft rolls.
| Room | No repeat |
|---|---|
| 10 × 10 ft | 8 rolls |
| 12 × 12 ft | 10 rolls |
| 12 × 14 ft | 11 rolls |
| 14 × 16 ft | 12 rolls |
Common mistakes to avoid
- Ignoring the pattern repeat — a 24 in repeat can mean one fewer strip per roll.
- Buying rolls from different batch numbers.
Frequently asked questions
Should I subtract doors and windows?
Usually not — the short strips above and below them still need full drops. Only skip wide, full-height openings.
What is pattern repeat?
The vertical distance before the design repeats. Each strip must start at the same point in the pattern, so larger repeats waste more paper.