Wallpaper Calculator
Enter the wall size, the roll size and the pattern repeat to see how many strips you'll hang and how many rolls to buy — the way installers calculate it.
Enter the wall size and the roll size.
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How to use the wallpaper calculator
- Choose a whole room or one wall and enter its size and the wall height.
- Skip full-height openings like doors and floor-to-ceiling windows by entering their total width. Leave smaller windows in: the offcuts above and below them are rarely usable.
- Select the roll size printed on the label and the pattern repeat — the vertical distance before the design repeats.
How wallpaper is calculated: the strip method
Dividing the wall area by the roll area underestimates, because the end of every roll is too short for a full strip. Installers count strips instead:
Worked example: a 12 × 10 ft room, 8 ft walls, one door, 20.5 in × 33 ft rolls
- Wall width: 44 ft − 3 ft door = 41 ft = 492 in → 492 ÷ 20.5 = 24 strips
- Strip length with no repeat: 96 + 0 + 4 = 100 in; a 396 in roll gives 3 strips
- Rolls: 24 ÷ 3 = 8 rolls
- With a 21 in pattern repeat, each strip is 121 in: still 3 per roll → 8 rolls. With a 36 in repeat, strips are 136 in and only 2 fit per roll → 12 rolls. A large repeat can add several rolls.
Roll sizes
| Roll | Typical size | Coverage |
|---|---|---|
| US single roll (priced by single, sold in doubles) | 20.5–27 in × 13.5–16.5 ft | 28–35 sq ft |
| US double roll | 20.5–27 in × 27–33 ft | 56–70 sq ft |
| European roll | 53 cm × 10 m (20.9 in × 32.8 ft) | about 57 sq ft |
In the US, wallpaper is often priced per single roll but only sold in double rolls. Check whether the listing's price and your calculation refer to singles or doubles.
Pattern repeat and match
- Random match: any strip lines up with any other — least waste. Enter 0.
- Straight match: the pattern lines up horizontally across strips; you lose up to one repeat per strip.
- Drop match: the pattern shifts half a repeat on alternate strips; plan for the full repeat per strip.
Frequently asked questions
How many rolls of wallpaper for a 12 × 12 room?
With 8 ft walls, one door and 20.5 in × 33 ft rolls with no repeat: 45 ft of wall width → 27 strips at 3 per roll → 9 double rolls.
Should I subtract windows?
Only large or full-height ones. Pieces above and below average windows are too short to use elsewhere, so they don't save rolls.
Should I buy an extra roll?
For patterned papers, yes — a spare from the same batch is valuable for mistakes and future repairs, and a later batch may not match.