KDP margin & gutter calculator
Enter a trim size and page count to get KDP's minimum margins, and the wider ones a well-made book uses.
| Edge | KDP minimum | Recommended | Why |
|---|
Why the gutter depends on your page count
A thicker book loses more of each page into the binding, so the minimum inside margin rises with page count. It is 0.375″ up to 150 pages, then 0.5″, 0.625″, 0.75″, and 0.875″ for the longest books.
A wider gutter fits less text per page. That adds pages, which can push the book into the next band. Lay the book out, read the real page count, adjust the margins and repeat until they agree. Near a band edge, use the wider gutter; it is valid on both sides.
The full KDP inside-margin table
| Page count | Minimum inside margin |
|---|
What bleed changes
Use bleed only if ink runs off the edge of the page. It does not change the trim size; it adds 0.125″ to the top, bottom and outside edges of the PDF page. Never add it to the spine edge, which is not cut.
Bleed also raises the minimum outside, top and bottom margins from 0.25″ to 0.375″, measured from the trimmed edge, not from the edge of the larger document. On a 6.125 × 9.25 bleed page, a 0.375″ top margin set from the document edge leaves only 0.25″ above the cut, which is under the minimum.
For a plain-text book, leave bleed off.
Aim above the minimum
KDP's numbers are the floor below which a book cannot be bound and trimmed reliably. A file set exactly at the floor meets the requirement, but looks cramped.
Well-made books use more, and not evenly: the bottom margin is deeper than the top, so the text sits slightly high, and the outside margin is wide enough for a thumb. The Recommended column follows those proportions.