Wallpaper match types — random, straight, and half-drop set the waste factor
How the repeat lines up at the seam is the match type, and it sets the default waste: random ≈10%, straight ≈15%, half-drop ≈20%. A bigger drop means more paper trimmed at the ceiling and floor to align the design.
What this diagram shows
Three side-by-side wall panels show how a wallpaper pattern lines up at the seam between two strips. In a random or free match the motif lands at any height, so adjacent strips need no alignment and waste is lowest, about 10 percent. In a straight match the same point of the pattern meets the ceiling on every strip, so the motif rows line up straight across the seam, wasting about 15 percent. In a half-drop match every other strip is dropped half a repeat, so a half-repeat is trimmed off the top of alternating strips to align the design, wasting about 20 percent. The bigger the offset you must trim away to align strips, the higher the waste factor.
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