Half Drop Wallpaper Calculator
Rolls and cuts for half-drop match.
Special
Wallpaper Roll Calculator
Count wallpaper the way installers do: by drops (full-height strips) per roll, not by square footage. Enter your walls, the roll size and the pattern repeat to see how many rolls to buy and exactly where each drop is cut.
How it works
- Add up the widths of the walls you are papering and enter the wall height.
- Enter the combined width of doors and other full-height openings.
- Choose the roll size and pattern match, and enter the pattern repeat from the label.
- Read the rolls to buy, the drops each roll gives and the cutting plan.
Formula
Drops = ⌈(wall width − full-height openings) ÷ roll width⌉ Drop length = wall height + trim allowance Straight match: each drop starts at a multiple of the repeat → ≈ ⌈drop length ÷ repeat⌉ × repeat per drop Rolls = drops cut in order until each roll runs out
Wallpaper must be hung in full-height strips (drops) whose pattern lines up across the seams. With a straight match every drop begins at the same point in the pattern; with a half drop, alternate drops begin half a repeat lower; random (free) match patterns can be cut anywhere. The calculator cuts drops from each roll in order, respecting the match, and counts how many rolls that uses. Roll presets: U.S. double roll 20.5 in × 33 ft, Euro roll 0.53 × 10.05 m, wide roll 27 in × 27 ft.
Example
A 12 × 14 ft bedroom (52 ft of wall) with 9 ft ceilings, one door and a closet (6 ft of full-height openings), papered with Euro rolls with a 25 in straight-match repeat.
Inputs
- Total width of walls
- 52 ft
- Wall height
- 9 ft
- Full-height openings
- 6 ft
- Roll size
- Euro roll (0.53 × 10.05 m)
- Pattern match
- Straight
- Pattern repeat
- 25 in
- Trim allowance per drop
- 4 in
Result
Rolls to buy9 rolls27 drops of 112 in · straight match
Drops needed27
Usable drops per roll3
Pattern-matching waste6.6%
Why square footage undercounts wallpaper
Dividing wall area by the area of a roll ignores two unavoidable losses: the part of each roll too short to make another full drop, and the paper skipped to line up the pattern. On a 33 ft roll and an 8 ft wall with a 21 in repeat, only three straight-match drops fit, so about a quarter of each roll is waste before a single cut goes wrong.
Large repeats and half-drop patterns waste the most. If the calculator shows high pattern waste, a roll with a smaller repeat — or a random-match design — can need noticeably fewer rolls for the same room.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 × 12 room?
A 12 × 12 room with 8 ft ceilings and one door has about 45 ft of wall to cover, or 27 drops of 20.5 in paper. With a 21 in straight repeat, a U.S. double roll yields 3 drops, so about 9 rolls. Enter your repeat for a precise count.
What does pattern repeat mean on wallpaper?
It is the vertical distance before the design repeats itself. Every drop has to start at a matching point, so paper is skipped between drops; larger repeats skip more.
Is a U.S. double roll twice a single roll?
Yes. In the U.S. wallpaper is often priced per single roll but sold in double rolls of about 56 sq ft. Enter the roll you actually buy.
Should I deduct windows?
Not usually. You still need drops above and below a window, often cut from the same roll. Deduct doors and floor-to-ceiling openings only.