Wallpaper Calculator
Total the wall widths, enter the wall height and your roll's label dimensions, and get a roll count computed the way paper actually hangs: whole strips, each cut to whole pattern repeats, from rolls that yield whole strips — with the naive area shortcut shown beside it so you can see the difference.
Walls and roll
Example: 40 ft of wall at 8.5 ft high, 20.5 in × 33 ft rolls with a 24 in repeat → 24 strips cut at 10 ft → 8 rolls.
Quantities only — surface prep, liner paper, and adhesive choice are between you, the manufacturer's instructions, and your decorator.
The strip math, spelled out
Strips first: 40 ft of wall is 480 in, and at 20.5 in per strip that is 24 strips (always rounded up — a
partial strip is still cut from a full length). Each strip must contain whole repeats: 8.5 ft is 102 in, and 102 ÷ 24 = 4.25 repeats, which rounds up to 5 — so every strip is cut at 10 ft, and the 1.5 ft above
each cut is unavoidable pattern-matching offcut. A 33 ft roll therefore yields
floor(33 ÷ 10) = 3 whole strips,
and 24 strips ÷ 3 =
8 rolls.
The naive shortcut — wall area (340 sq ft) divided by roll face area (56.38 sq ft) — says 7 rolls. It is wrong in the dangerous direction: it spends the repeat offcuts and the end-of-roll remainders as if they were usable paper. Dye lots make under-ordering doubly expensive, because a top-up roll bought later may not match the batch on your walls.
Other ways to cover the same walls
Painting instead? The paint calculator works the same walls by area and coats. If the room is still at the framing stage, count the substrate with the drywall calculator first — and its openings logic explains the same door-vs-window subtleties from the hanging side.
Frequently asked questions
Why not just divide wall area by roll coverage?
Because paper hangs in full-height strips, and strips do not tessellate like paint. With a 24 inch repeat on an 8½ foot wall, every strip must be cut at 10 feet (five repeats) so the pattern matches at the seams — and a 33 foot roll then yields exactly 3 whole strips, not 3.9. The area shortcut hides both losses; on this page’s worked example it says 7 rolls when the honest count is 8, and 7 runs out of paper.
What is a pattern repeat, and where do I find it?
The vertical distance before the printed design recurs, listed on every roll label and product page (for example "repeat: 24 in / 61 cm"). Enter 0 for plain, textured, or free-match papers — strips are then cut at the wall height with no rounding. Half-drop patterns effectively behave like a larger repeat; when in doubt, enter the full repeat and treat the answer as the safe count.
Why do I enter the roll size myself?
Because US wallpaper has no single roll: 20.5 and 27 inch widths, single rolls around 16.5 feet and double rolls around 33, European metric sizes — coverage claims run anywhere from about 28 to 70 square feet per roll depending on the product. The two numbers on your label are the only honest inputs, so that is what the tool asks for.
How do I handle doors and windows?
Only full-height openings save paper. A doorway that runs floor to ceiling means strips simply are not hung there — enter its width in the openings field. A window does NOT usually save a strip: the strip still hangs above and below it, cut from the same full-length piece, so leave windows out and enjoy the offcuts as patch material.
Where is the waste percentage field?
Deliberately absent. In strip math the waste is already computed explicitly: the repeat rounding on every strip and the unusable remainder at the end of each roll. Adding a percentage on top would double-count the margin. If you want protection against damage or a future repair, add a roll — knowingly, not through a hidden fudge factor.
Wall measurements never leave your browser. The strip-based method and its tests are documented on the methodology page.