Web fiction
Trim size
The finished page size a printed book is trimmed to after binding; set it first, because margins, bleed and page-count limits all depend on it.
Trim size is the size a printed book's pages are cut to after binding: KDP defines it as "Your printed book's width and height." It comes first because everything else hangs on it: KDP's instruction is "Set your trim size before you set your margins," since margin size depends on page count and on whether elements bleed. KDP's standard paperback trims include 5" x 8", 5.06" x 7.81" (12.9 x 19.8 cm) and 6" x 9" (15.24 x 22.86 cm), which KDP calls the most common trim size for books in the US.
For the author, trim is the first layout decision, because changing it after typesetting reflows every page; the gutter minimum, bleed setup and the page-count range all follow from it. A trim can be an identity as much as a size: the bunkobon standard behind the A6 bunko page format. The full walkthrough is how to create a print-ready PDF.
Sources
- Amazon KDP help: Set Trim Size, Bleed, and Margins fetched 2026-10-14