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Redmoon Calculators
Maker & workshop

Wallpaper Calculator with Pattern Repeat

Free wallpaper roll calculator with pattern repeat support. Enter each wall's width, the height, roll size, pattern repeat and match, and a trim allowance to get the number of rolls needed, counted wall by wall, including door/window deductions and a waste buffer.

Built and maintained by Paul Clark, Redmoon Software · Last verified · Sources · Changes and corrections

When to use this

Use before ordering wallpaper for a full room, especially with a bold pattern that has a visible repeat — it prevents an expensive mid-job reorder from a different dye lot.

How it compares

Many wallpaper calculators ignore pattern repeat, trim and wall-by-wall counting, quietly underestimating rolls. This one builds all three into the drop math.

Enter your values below. Calculations run locally as you type.

Room & roll

Rolls needed

Rolls to buy
10
26 drops needed
Drops per roll
3
cut length 100.0"
Strips deducted
0
for 0.0 sq ft openings

4 walls (480" in all) take 8 + 5 + 8 + 5 = 26 drops, counted wall by wall (24 if every corner offcut could start the next wall). Each drop is 96.0" of wall plus 4.0" trim: 100.0", so a 33.0 ft roll gives 3. Buy 10 rolls, all from the same batch (dye lot).

How it works

Each drop is cut to the wall height plus a trim allowance (4 inches by default, about 2 at the ceiling and 2 at the baseboard, as York Wallcoverings advises). With a straight match that length is rounded up to whole pattern repeats; with a half-drop match it is rounded up to the next point half a repeat past a whole one, because alternate drops start half a repeat lower.

Drops per roll = roll length ÷ cut length, rounded down. Drops needed are counted wall by wall (each wall's width ÷ roll width, rounded up, because a wall's last part-width strip is still a full drop), minus any whole strips saved by large door/window openings.

Rolls needed = (net drops ÷ drops per roll), inflated by your waste buffer percentage and rounded up to a whole roll.

FAQs

Why does a pattern repeat increase how much wallpaper I need?

A pattern repeat forces every drop to start at the same point in the design, so each cut strip must be rounded up to the next full repeat length rather than the exact wall height. That shortens how many usable drops you get from each roll, which is why large repeats can noticeably increase the total rolls needed.

Why buy all my rolls from the same dye lot or batch?

Wallpaper color and pattern alignment can shift subtly between production runs, even for the identical SKU. Buying every roll for a room from a single batch avoids visible seams or color banding where a later-purchased roll meets an earlier one.

How do I enter the walls?

Measure each wall you're covering and enter the widths as a list, such as 144, 96, 144, 96. The calculator counts drops wall by wall, because the last strip on each wall is a full-length drop even if only part of its width is used. Where walls meet at a corner you can sometimes hang that strip's offcut on the next wall, so the result also shows the lower count you would get if every offcut could be reused. Enter door and window openings in the deduction field instead of subtracting them from a wall's width.

Why add a trim allowance?

Each drop is hung slightly long and trimmed against the ceiling and baseboard, because neither is perfectly straight. York Wallcoverings suggests about 4 inches per drop, 2 at each end, which is the default. It matters more than it looks: on 8-foot walls a 33-foot roll gives four 96-inch drops on paper but only three once 4 inches of trim are added.

Worked example

Input

Walls of 144, 96, 144 and 96" (a 12 × 8 ft room), 96" wall height, 4" trim, 20.5" roll width, 33 ft roll length, no pattern repeat, 0 sq ft deducted, 10% waste.

Output

10 rolls needed (26 drops, 3 per roll).

Cut length = 96 + 4 = 100" (no repeat). Drops per roll = floor(396/100) = 3. Drops counted wall by wall: 8 + 5 + 8 + 5 = 26 (24 if every corner offcut could start the next wall). Rolls = ceil((26/3) × 1.10) = ceil(9.53) = 10.

Common pitfalls

  • A large pattern repeat can dramatically cut usable drops per roll — always enter the repeat and its match type even if it seems minor.
  • Setting the trim allowance to 0 makes the count look smaller than what you can actually cut: on 8 ft walls it is the difference between 4 and 3 drops per roll.
  • Deducting door/window area only saves whole strips, so small openings inside a strip won't reduce the roll count.
  • Always round up and buy from a single batch — reordering later risks a visible dye-lot mismatch.

Pattern repeat drives the roll count

For a plain paper, rolls needed follows from wall area and roll dimensions. For a patterned one it does not, because each drop must start at the right point in the pattern, and the offcut above that point is waste. The longer the repeat, the more waste per drop.

A large repeat can push usable drops per roll from three down to two, which is a 50% increase in rolls for the same wall. The trim allowance works the same way: 96-inch walls get four drops from a 33-foot roll on paper, but 96 inches plus 4 of trim gets three.

Straight against drop match, and buying in one batch

A straight match aligns the pattern at the same height on every drop. A half-drop match offsets alternate drops by half the repeat, so each drop, cut in turn from the roll, runs to the next point half a repeat past a whole one. Depending on the wall height that wastes less or more than a straight match: with a 27-inch repeat, a 112-inch cut uses 135 inches straight but 121.5 half-drop, while a 100-inch cut with a 21-inch repeat uses 105 straight and 115.5 half-drop. The calculator does this arithmetic for whichever match you pick, which is easy to get wrong by hand.

Buy every roll from one batch. Batch numbers exist because colour varies measurably between print runs, and a mismatched roll in the middle of a wall is visible under raking light even when it looks identical in the shop.

Read more about this

· 7 min read

Dye lots, deductions, and the waste buffer: ordering wallpaper you won't have to reorder

Getting the roll count right is only half the wallpaper order. The other half is buying from one dye lot, setting a sane waste buffer, and deducting doors and windows without shorting yourself.
· 9 min read

Wallpaper math: why pattern repeat changes how many rolls you need

How a pattern repeat forces every wallpaper drop to round up to the next full repeat length, cutting usable drops per roll — with a before/after example showing exactly how many more rolls it costs.

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