Wallpaper Calculator
Enter the room size, the wall height and the size of your roll to see how many strips and rolls you need. Add the pattern repeat and a trim allowance, and the calculator rounds up to whole rolls.
Last updated November 4, 2026
Counted as a width of wall you can skip. A rough estimate, so leave blank to be safe.
Typical: 20.5 in (US) or 53 cm. Check the label.
Typical: 33 ft (US) or 10.05 m. Check the label.
0 for a plain or random-match paper.
Extra length per strip for trimming; 4 in (10 cm) is typical.
Result
11 rolls
| Measure | Value |
|---|---|
| Wall width to cover | 624 in |
| Strips needed | 31 |
| Length of one strip | 100 in |
| Strips per roll | 3 |
| Rolls (rounded up) | 11 |
| Spare strips | 2 |
Estimate by the strip method. Roll sizes and pattern matching vary, so check the label and buy all rolls from one batch.
Show the work
Formula: strips = ceil(wall width / roll width); strips per roll = floor(roll length / (height + repeat + trim)); rolls = ceil(strips / strips per roll)
- Perimeter: 2 x (14 + 12) = 52 ft = 624 in.
- Strips: 624 / 20.5 in roll width, rounded up = 31.
- Strip length: 96 + 0 repeat + 4 trim = 100 in.
- Strips per roll: 396 in roll / 100, rounded down = 3.
- Rolls: 31 / 3, rounded up = 11.
Result: 11 rolls
How the number of rolls is worked out
strips = ceil( wall width ÷ roll width )
strips per roll = floor( roll length ÷ (height + repeat + trim) )
rolls = ceil( strips ÷ strips per roll )
Wallpaper hangs in vertical strips. The strip count is the total wall width divided by the roll width, rounded up. Each strip is as long as the wall plus the pattern repeat and a trim allowance, and a roll yields only whole strips, so the strips per roll are rounded down.
A 14 ft by 12 ft room has 52 ft of wall, or 624 in. With 20.5 in rolls that is 624 ÷ 20.5 = 30.4, so 31 strips. For 8 ft walls and a 4 in trim, each strip is 100 in, and a 33 ft (396 in) roll gives 3 strips. Then 31 ÷ 3 = 10.3, so 11 rolls.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Roll size, repeat and trim
The defaults of 20.5 in by 33 ft (US) and 53 cm by 10.05 m (metric) are typical sizes, but rolls vary, so enter the figures from your label. Set the pattern repeat to 0 for a plain or random-match paper. The trim allowance of 4 in (10 cm) is a typical default.
Doors and windows
The openings field turns an area into an equivalent width of wall by dividing by the wall height. It is a rough estimate, because paper is still needed above and below doors and windows. Leave it blank for a safe count.
How to use the Wallpaper Calculator
- Choose imperial or metric, then enter the room length and width or the total wall width.
- Enter the wall height and, if you like, the area of doors and windows.
- Enter the roll width and length from the label.
- Set the pattern repeat and trim allowance.
- Read the strips and rolls, then use Copy, Print or Share.
Worked example
A 14 ft by 12 ft room has 624 in of wall and needs 31 strips of 20.5 in. With 8 ft walls and 4 in of trim, a 33 ft roll gives 3 strips, so 31 ÷ 3 = 10.3 rounds up to 11 rolls.
| Walls | Strips | Per roll | Rolls |
|---|---|---|---|
| 40 ft around, 8 ft high | 24 | 3 | 8 |
| 52 ft around, 8 ft high | 31 | 3 | 11 |
| 52 ft, 40 sq ft of openings | 28 | 3 | 10 |
| 52 ft around, 9 ft high | 31 | 3 | 11 |
Frequently asked questions
How many rolls of wallpaper do I need?
Divide the wall width by the roll width for strips, find how many strips fit on a roll, then divide. A 14 ft by 12 ft room with 8 ft walls needs 11 US rolls.
How does the pattern repeat change the amount?
Each strip gets longer by the repeat, so fewer strips fit on a roll. A bigger repeat can mean an extra roll or more.
Should I subtract doors and windows?
The calculator can, but only as a rough width, and paper is still needed above and below. Leaving it blank gives the safer count.
Should I buy extra rolls?
Many people add a spare roll for mistakes and repairs, and buy all rolls from the same batch so colors match.