Wallpaper Calculator
Count strips, not square feet — rolls needed for your perimeter, roll size and pattern repeat, with doors and windows handled.
Count strips, not square feet — rolls needed for your perimeter, roll size and pattern repeat, with doors and windows handled.
Total width of openings to skip. Set 0 to paper over them.
Length of one full pattern cycle. 0 = no matching.
Roll size
Enter your room's perimeter and height to count rolls.
Frequently asked questions
How many rolls of wallpaper do I need?
Count strips, then rolls — never square feet. A room with a 44-foot perimeter and 8-foot walls, using a standard US double roll of 20.5 in × 33 ft with no pattern matching, needs 26 strips; each roll yields 4 strips, so you buy 7 rolls. The strip method automatically prices in the fact that a 40-inch leftover is useless for an 8-foot wall, which area-based math happily ignores — and which the store will not refund.
How does pattern repeat change the count?
Every strip must start at the same point in the pattern, so each strip consumes wall height plus up to one full repeat. With a 24-inch repeat on 8-foot walls, the usable strip grows from 96 to 120 inches: a US roll now yields 3 strips instead of 4, and the same 44-foot room needs 9 rolls instead of 7. That is a 30% budget jump from pattern alone, which is why the repeat length belongs on your shopping list, not just the color.
US vs European roll sizes?
A US double roll is 20.5 inches wide and 33 feet long; a European roll is 0.53 m wide and 10.05 m long — nearly the same area, cut into different proportions. EU rolls are slightly wider and slightly shorter in imperial terms (about 20.9 in × 33 ft), so strip counts come out within a roll of each other on most rooms. What matters is that you do not mix them on one wall: the seams and pattern rhythm differ noticeably.
Should I subtract doors and windows?
Usually yes, moderately. Openings do not need paper, so a 6-foot doorway total removes 6 feet from the perimeter — the 44-foot room drops to 23 strips and one fewer roll. But keep expectations calibrated: above a door or window you still hang short strips, and pattern matching often burns the saving. The calculator subtracts full opening width; if you would rather paper over framing and trim later, set openings to zero.
What is half-drop match?
A half-drop pattern shifts the design down by half a repeat on every other strip, so adjacent strips interlock like brickwork instead of mirroring at the same height. It is the more wasteful of the two match styles. This calculator approximates both straight and half-drop matches with the same rule — budget one full repeat of allowance per strip — which is deliberately conservative for half-drop and exactly right for straight match.
Why strip-based beats area-based
Wallpaper is not paint: you cannot buy 4.6 rolls the way you buy 4.6 liters. Rolls come whole, cut into vertical strips the height of your wall, and every strip must be cut from one continuous piece with its pattern aligned. Area math — perimeter times height divided by roll coverage — quietly assumes you can stitch leftovers together like quilt patches. In reality, a leftover 40 inches short of the ceiling is waste, and area math systematically undercounts it.
The strip method mirrors how professionals actually order. Divide the net perimeter by the roll width and round up: that is how many strips the room hangs. Divide the roll length by the usable strip length and round down: that is how many strips each roll yields. Divide the two and round up: rolls to buy. Every rounding step errs on the side of having paper left over, because dye-lot matching is real — the roll you go back for next week will not quite match the one on your wall.
The 44 × 8-foot example shows the whole pipeline: 44 ft of perimeter ÷ 20.5 in of width = 25.76, so 26 strips; 396 in per roll ÷ 96 in per strip = 4.1, so 4 strips per roll; 26 ÷ 4 = 6.5, so 7 rolls. The same room with 6 feet of openings drops to 23 strips and 6 rolls. Buy from the same dye lot, keep one unopened roll for future repairs, and return nothing.
Pattern repeat and the one-repeat allowance rule
When a design repeats every R inches along the roll, strips must be cut so the pattern lands at the same height on every strip. The practical rule: cut every strip to wall height plus one full repeat, then slide the strip to align the pattern and trim the excess at ceiling line. Over a whole room you lose at most one repeat per strip, and usually a bit less — the allowance is the worst case that keeps you from a mid-wall mismatch.
Small repeats barely register: a 6-inch repeat on 8-foot walls stretches the usable strip about 6%, often costing no extra roll. Large repeats bite hard — the 24-inch repeat example moved the room from 7 rolls to 9. Before falling for a big-impact pattern, run it through the calculator twice, once with repeat zero and once with the real number; the difference is the true price of the design.
One honest limitation: half-drop matches, where alternate strips start half a repeat lower, can need a second half-repeat on some strips. This tool budgets a full repeat for every strip regardless — identical to the straight-match rule — which is exact for straight matches and conservative (slightly over) for half-drop. If the calculator says 9 rolls for a half-drop paper, 9 rolls is a safe buy, not a stretch.
Reading a roll label: US vs EU
US labels quote a double roll as 20.5 in × 33 ft — width first, then length. European labels read 0.53 m × 10.05 m, the same two numbers in metric dress. The calculator's presets encode exactly these dimensions; if your label says something else (grasscloth panels, mural sets, 36-inch designer widths), switch to Custom and type the label's numbers in your current units.
Watch one trap when comparing prices across the two standards: quote per-roll prices only after normalizing to strips-per-roll for your wall height. On 8-foot walls both standards yield 4 strips per roll without repeat, so a pricier EU roll that yields the same count may actually be the better buy per strip. The calculator's strips-per-roll line makes that comparison direct — bring it to the store.
Estimates assume plumb walls and consistent pattern alignment. Order from a single dye lot and keep an unopened roll for repairs.
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