Rolls and the pattern-match trap
Wallpaper is sold in single (about 36 sq ft) or double rolls, but <strong>usable coverage is less once the pattern repeat is cut away</strong> — a 20.5-inch repeat can drop usable yield to 27 sq ft or less per double roll. The calculator sizes wall area into rolls; subtract the repeat allowance from the roll coverage stated on the label.
Book the drops, hang them rested
Each cut length ('drop') is pasted, folded book-style and rested a few minutes to relax. Pattern repeats mean alternating drops hang upside down in some patterns, and hang order must continue around the room from the same bolt. As with brick: one dye lot, ordered all at once.