Calculate rolls of wallpaper needed for any room with pattern repeat and obstacle adjustments.
This tool estimates how many rolls of wallpaper a room needs. It sums wall area from the room's perimeter and wall height, subtracts doors, windows, and other openings, applies waste tied to the pattern repeat, and rounds up to whole rolls. The pattern repeat surprises most people: every vertical strip must start at the same point on the pattern, so a strip's usable length is the wall height rounded up to a whole number of repeats, and top-and-bottom trimming comes out of the roll too. Dividing wall area by the coverage printed on the roll label ignores that waste and can understate an order by a roll or two.
A concrete input and expected output from the current implementation.
Input
Room: 12 ft by 10 ft, walls 8 ft high; one door 3 ft by 7 ft\nRoll: 20.5 in wide by 33 ft long (single roll)\nPattern repeat: 24 in
Expected output
7 rolls
Wall area is 44 ft of perimeter times 8 ft, or 352 sq ft, and the door subtracts 21 sq ft, leaving 331 sq ft. Each roll yields four drops of 20.5 by 96 in (54.7 sq ft) because the 24 in repeat divides the 96 in height exactly, and 331 divided by 54.7 is 6.05, rounded up to 7; a strip-count check (26 drops at four per roll) gives the same answer.
Wall area comes from the room perimeter times wall height, using the width you enter for each wall. Door, window, and other opening areas are subtracted from the total, but an opening never saves its full area: the strip that crosses the space above a door or below a window still has to be cut from a roll. The remainder is divided by usable area per roll.
A strip's usable length is the wall height rounded up to a whole number of repeats, because every drop must start at a matching pattern point and the mismatch is trimmed. A 93-inch wall with a 24-inch repeat takes 96 inches of roll, losing 3 inches per strip. A 20.5 by 396 inch single roll then yields four drops, about 54.7 square feet of coverage against 56.4 of nominal area.
Experienced paperhangers do, and it can save most of a roll on a busy room, but it depends on the pattern. Pieces join cleanly only where the pattern lines up across the seam, so with a 24-inch repeat the saving is small. If you plan to piece, start from the tool's count and only drop a roll after seeing how the drops actually fall.
Yes to the extra roll, with a caveat on returns. Beginners typically waste part of one or two rolls, so ordering one extra is standard advice. Whether it is returnable depends on the store and on the roll staying unopened. Check the dye-lot number on the label too: rolls from a different batch can be visibly different, which is why you want the spare before you start.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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