Wallpaper strip yield — every strip rounds up to a whole pattern repeat

What this diagram shows

A diagram shows why wallpaper uses more than the bare wall area. Each vertical strip must be cut to a whole number of pattern repeats so the motif lands at the same height on the next strip, so the strip length is the ceiling height plus a 4-inch trim allowance rounded up to the next full repeat, and the leftover chunk is trimmed off and thrown away on every strip. For a 9-foot ceiling that is 112 inches, and with an 18-inch repeat it rounds up to seven repeats, or 126 inches — a 10.5-foot strip with 1.17 feet of trim waste. A 33-foot bolt then yields only three usable strips, with a 1.5-foot tail too short to use. Random or textured paper with no repeat skips the rounding and yields four strips per bolt.