Wallpaper Calculator
Updated 2026-10-14
Wallpaper is hung in vertical strips, so the most reliable way to estimate it is to count strips, not square feet. Enter your walls and the roll details from the label, and the calculator tells you how many rolls to buy.
How the wallpaper calculator works
Square-foot estimates for wallpaper are often wrong, because the leftover piece at the end of each roll is usually too short to use. Counting strips avoids that problem. The calculator works out how many strips cover your walls, how long each strip must be, and how many whole strips you can cut from one roll.
Strip length = wall height + trimming allowance (rounded up to a whole pattern repeat)
Strips per roll = roll length ÷ strip length, rounded down
Rolls = strips ÷ strips per roll, rounded up
The calculator adds 4 inches (10 cm) to every strip so you can trim it neatly at the ceiling and baseboard. Windows are not subtracted, because you still need paper above and below them, and the offcuts rarely fit anywhere else.
Worked example
A 12 × 10 ft bedroom has 44 ft of wall. Take away one door (3 ft) and 41 ft remains, which is 492 inches. With 20.5 inch wide paper, that's exactly 24 strips. Each strip needs to be 8 ft plus 4 inches for trimming, or 100 inches. A 33 ft roll is 396 inches long, so it gives 3 full strips. 24 strips ÷ 3 per roll = 8 rolls.
What is pattern repeat?
Patterned wallpaper has to line up from one strip to the next. The pattern repeat is the distance before the design starts again, printed on the label in inches or centimeters. Each strip must start at the same point in the pattern, so the strip length is rounded up to a whole number of repeats. A large repeat can easily add one or two rolls to a room.
| Match type | What it means | Extra paper |
|---|---|---|
| Free or random match | No pattern to line up (plain, textured, stripes) | Least |
| Straight match | The pattern lines up straight across each strip | Up to one repeat per strip |
| Drop (offset) match | The pattern lines up halfway down the next strip | Often the most; buy an extra roll |
Roll sizes
Roll sizes vary by brand and country, so always use the numbers on the label. A common size in Europe, the UK and Australia is about 53 cm wide and 10.05 m long. In the US, many papers are sold in "double rolls", for example 20.5 inches wide by 33 feet long, though prices are sometimes quoted per single roll. If the label shows a double roll, enter the full double-roll length and count the result as double rolls.
Tips before you buy
- Check the batch number. Colors can vary slightly between print runs. Buy all your rolls with the same batch (lot) number.
- Buy a spare. An extra roll covers mistakes and future repairs. Many stores take back unopened rolls; ask before you buy.
- Feature wall only? Enter just that wall's width and set doors to 0.
- Sloped ceilings and stairwells need extra. Measure the tallest point for every strip, or ask your supplier to check your estimate.
Frequently asked questions
- How many rolls of wallpaper do I need for a 12 × 12 room?
- With 8 ft walls, one door, plain 20.5 inch paper and 33 ft rolls, you need 27 strips (48 ft of wall less 3 ft for the door), at 3 strips per roll, so 9 rolls.
- How many rolls for a feature wall?
- A wall 3.6 m wide and 2.4 m high, with plain 53 cm × 10.05 m rolls, needs 7 strips. Each strip is 250 cm with trimming, so a roll gives 4 strips, and you need 2 rolls.
- Should I subtract windows?
- Usually not. You still paper above and below most windows, and the cut-out piece is normally too small to reuse. Ignoring windows also gives you a sensible safety margin.