Wallpaper Calculator
Enter your walls, doors and windows, choose a roll size and the pattern repeat, and see how many rolls to buy, how many strips to cut and how long each strip should be.
Walls
Doors & windows (not papered)
Roll & pattern
Estimate only. Buy all rolls from the same batch (lot) number and check the label for the exact repeat and match.
Breakdown by wall
| Wall | Width | Area | Full-height strips |
|---|
How to use the Wallpaper Calculator
- Pick your units: feet and inches or meters and centimeters.
- Enter the wall height and the width of each wall, or use the rectangular room helper to fill in four walls at once.
- Add doors and windows with their size and count so they are deducted.
- Choose the roll size and enter the pattern repeat and match type from the wallpaper label.
- Press Calculate rolls to see the rolls to buy, the strips per roll and the cut length of each strip.
How the wallpaper roll calculation works
Wallpaper is hung in vertical strips, so the calculator counts strips, not square feet:
- Cut length = wall height + trim allowance (about 4 in or 10 cm). With a pattern, round it up to the next whole repeat; for a half-drop match add another half repeat.
- Strips per roll = roll length ÷ cut length, rounded down.
- Strips per wall = wall width ÷ roll width, rounded up.
- Doors and windows: their total area divided by the area of one full strip, rounded down, is subtracted.
- Rolls = strips ÷ strips per roll × (1 + waste %), rounded up.
Worked example: four walls of 12, 12, 10 and 10 ft, 8 ft high, one 3 × 6.8 ft door and two 3 × 4 ft windows, US double rolls (20.5 in × 33 ft) with a 21 in straight-match repeat. Cut length = 96 + 4 = 100 in, rounded up to 5 repeats = 105 in, so 396 ÷ 105 = 3 strips per roll. The walls need 8 + 8 + 6 + 6 = 28 strips; the openings (6,394 sq in) save 3 strips, leaving 25. 25 ÷ 3 = 8.33 rolls, plus 10% waste = 9.17, so buy 10 rolls.
Standard wallpaper roll sizes
| Roll type | Width | Length | Coverage |
|---|---|---|---|
| US single roll | 20.5 in | 16.5 ft | about 28 sq ft |
| US double roll | 20.5 in | 33 ft | about 56 sq ft |
| US wide double roll | 27 in | 27 ft | about 60 sq ft |
| European standard roll | 53 cm (20.9 in) | 10.05 m (33 ft) | 5.33 m² (57 sq ft) |
| Wide roll | 70 cm | 10.05 m | 7.0 m² |
| Extra wide (non-woven) | 106 cm | 10.05 m | 10.65 m² |
Most US wallpaper is priced per single roll but sold only in double rolls. Always check the label: widths and lengths vary by brand.
How pattern repeat affects waste
The bigger the repeat, the more paper is lost at the top or bottom of each strip. Strips per 33 ft double roll with 4 in of trim:
| Repeat | Match | Cut length, 8 ft wall | Strips/roll, 8 ft | Strips/roll, 7 ft |
|---|---|---|---|---|
| None | Random | 100 in | 3 | 4 |
| 12 in | Straight | 108 in | 3 | 4 |
| 21 in | Straight | 105 in | 3 | 3 |
| 21 in | Half-drop | 115.5 in | 3 | 3 |
| 25 in | Straight | 100 in | 3 | 3 |
| 27 in | Half-drop | 121.5 in | 3 | 3 |
On lower walls the repeat matters more: a 7 ft wall with no repeat fits 4 strips per double roll, but a 21 in repeat drops that to 3, which means a third more rolls. Tip: start the first strip in the corner least visible from the door, and use the leftover pieces above doors and below windows.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 × 12 room?
With 8 ft walls, US double rolls (20.5 in × 33 ft), no pattern repeat, one door and one window, you need 32 strips minus 2 saved by the openings, so 30 strips cut at 8 ft 4 in. Each roll gives 3 strips, so that is 10 rolls, or 11 rolls with 10% extra for waste.
What is a pattern repeat?
It is the vertical distance before the design repeats itself, printed on the label in inches or centimeters. Every strip has to start at the same point in the pattern, so strips are cut to a multiple of the repeat and the leftover piece is wasted.
What is the difference between straight match and half-drop match?
With a straight match the pattern lines up horizontally on every strip. With a half-drop match every other strip is shifted down by half a repeat, so you lose an extra half repeat per strip. Random or free match papers, like stripes or textures, have no repeat waste.
How big is a roll of wallpaper?
US rolls are usually 20.5 to 27 in wide and sold as double rolls of about 56 sq ft (33 ft long). European rolls are typically 53 cm wide and 10.05 m long, about 5.3 m², and wide rolls are 70 cm or 106 cm.
Why does the calculator count strips instead of area?
Wallpaper is hung in full-height strips and you cannot join short leftovers in the middle of a wall. Dividing area by roll coverage underestimates the rolls you need, so the area-only figure is shown just for comparison.
How much extra wallpaper should I buy?
Add 10 to 15% for mistakes, trimming and future repairs, and buy all rolls from the same batch number because colors can vary slightly between batches.