Wallpaper estimates go wrong when they are done by area alone. The paper is hung in vertical strips, each strip has to be cut so the pattern lines up with its neighbor, and the leftover at the end of each roll is often too short to use. This calculator uses the strip method that paperhangers use: count the strips around the room, work out how many full-height strips each roll yields for your pattern repeat, and divide.
How to use the wallpaper calculator
- Choose US or Metric units.
- Select Whole room and enter the length, width and wall height, or Wall width for a single accent wall.
- Enter the number of doors with their width and the number of windows with their area.
- Choose a roll size — a US double roll, a Euro roll, a wide roll or a custom size.
- Pick the pattern match and enter the repeat from the label.
- Check the trim allowance, the extra length on each strip for trimming at ceiling and baseboard.
The strip method
Doors are deducted by their full width. Windows are converted to an equivalent width (area ÷ wall height), because the short pieces above and below a window usually come from offcuts.
Worked example: a 12 × 14 ft bedroom
Perimeter: 2 × (12 + 14) = 52 ft. Minus a 3 ft door and two 15 ft² windows (30 ÷ 8 = 3.75 ft) leaves 45.25 ft = 543 in.
Strips: 543 ÷ 20.5 = 26.5 → 27 strips.
Strip length: 96 in wall + 4 in trim = 100 in, rounded up to five 21-inch repeats = 105 in.
Each 33-ft (396 in) roll gives ⌊ 396 ÷ 105 ⌋ = 3 strips, so 27 ÷ 3 = 9 double rolls, or 10 with a spare.
By area alone the same walls (362 ft²) would seem to need only 6.4 rolls. The difference is the pattern and the roll ends: each roll leaves an 81-inch piece that is too short for a full strip.
How wall height and repeat interact
The number of strips per roll changes in steps, so a small change can matter a lot. In the example room, a paper with a random match and a 3-inch trim allowance needs 99-inch strips, and a 396-inch roll yields exactly four of them — 7 rolls instead of 9. A 9-foot ceiling, on the other hand, drops most patterned papers to three strips per roll or fewer. If you are choosing between two papers you like equally, compare the roll counts for both repeats before you order.
| Repeat | Match | Typical extra paper |
|---|---|---|
| 0 (random or stripes) | Free | Least; strips can be cut back to back |
| Under 6 in (15 cm) | Straight | Small |
| 18–27 in (45–69 cm) | Straight | Moderate to large |
| Any | Half-drop | Adds about half a repeat per strip |
Hanging and buying tips
- Check batch numbers. Make sure every roll carries the same batch or dye-lot number.
- Prepare the walls. Prime new drywall with a wallpaper primer so the paper can be removed later without tearing the paper face of the board.
- Start in an inconspicuous corner, because the last strip rarely matches the first perfectly.
- Number your strips as you cut them so you hang them in order and keep the pattern consistent.
If you are only papering one accent wall, use the Wall width option and plan to paint the rest of the room with the paint calculator. For walls with odd shapes, total the widths with the feet and inches calculator first.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 × 12 room?
With 8-foot walls, one door and two windows, about 41 feet of wall needs 25 strips of 20½-inch paper. With a 21-inch straight-match repeat each strip is cut to 105 inches, so a 33-foot double roll yields three strips and you need 9 double rolls, plus a spare.
What is a pattern repeat?
It is the vertical distance after which the design starts over, printed on the roll label in inches or centimeters. Every strip has to start at the same point in the pattern (or half a repeat lower for a drop match), so strips are cut in whole repeats and the larger the repeat, the more paper is wasted.
What is the difference between a straight match and a half-drop match?
In a straight match, the design lines up horizontally across every strip. In a half-drop match, each strip is shifted down by half a repeat, which creates a diagonal rhythm. Half-drop papers waste a bit more because alternate strips start halfway through the repeat.
Is wallpaper sold in single or double rolls?
Most American wallpaper is priced per single roll but sold in double-roll bolts about 20½ inches wide and 33 feet long, roughly 56 ft². European rolls are about 53 cm by 10 m, close to the same area. This calculator works in whole rolls of the size you select.
Should I buy an extra roll of wallpaper?
Yes. Rolls are printed in batches (dye lots) whose color can differ slightly, so a matching roll may be impossible to find later. One spare roll from the same batch covers mistakes during hanging and future repairs.