Estimate how many rolls of wallpaper you need from your wall area, minus openings, with extra for pattern matching.
rolls = (wall_area − openings) ÷ roll_coverage × (1 + waste)
Subtract openings from the wall area, divide by the coverage per roll, and add waste — patterns need 15% or more for matching.
Large pattern repeats waste more paper. Check the repeat on your roll and increase waste accordingly.
Walls: perimeter 48 ft x 9 ft = 432 square feet. Subtract a door and window, about 40 square feet, for 392 square feet. A standard double-roll covers about 56 usable square feet, so 392 ÷ 56 = 7 rolls before waste, and at 15% pattern-matching waste about 8 rolls.
The waste factor is higher for wallpaper than paint because every strip must align with its neighbor. The bigger the pattern repeat, the more you trim to match — a large repeat can push waste to 20-25%, so check the repeat distance on the roll.
A standard double-roll covers about 56 ft² usable. Pattern matching drives the higher 15% waste — confirm your roll's coverage.
The pattern repeat is the vertical distance before the design starts over. To align the pattern between strips, each strip is cut at a multiple of the repeat and the offcut discarded — so a large repeat means more waste. A small or random repeat wastes little; a half-drop match or a large repeat can add 25% or more to your roll count. Read the repeat on the roll label and increase the order accordingly.
Wallpaper is priced in single rolls but often sold as double or triple bolts that yield fewer wasted end-cuts. Whichever you buy, order the whole job from one batch (run number) — like flooring dye lots, different batches vary slightly in color and show as banding on the wall. Buy a spare roll up front rather than topping up mid-job from a different batch.
Divide your net wall area by the roll's usable coverage and add 15% for pattern matching.
Cut each strip to the next multiple of the repeat above your wall height, discarding the offcut. A large repeat or half-drop match can add 25% to 70% to the paper needed, so increase your roll count beyond the bare area calculation.
Divide the wall area, minus large openings, by the usable coverage per roll (often about 25 sq ft from a single roll), round up, then add for the pattern repeat.
Subtract large openings such as doorways and picture windows, but leave standard windows and switch plates in, since the paper is cut around them and the offcuts cannot be reused.