The numbers
| Page count | Minimum inside margin | Metric |
|---|---|---|
| 24–150 | 0.375 in | 9.6 mm |
| 151–300 | 0.5 in | 12.7 mm |
| 301–500 | 0.625 in | 15.9 mm |
| 501–700 | 0.75 in | 19.1 mm |
| 701–828 | 0.875 in | 22.3 mm |
Outside, top and bottom margins: at least 0.25 in, or 0.375 in with bleed.
Which side the gutter is on
Page 1 of a printed book is a right-hand page (recto), so odd pages have their gutter on the left and even pages (versos) on the right. Layout programs call this mirrored or facing-page margins. A PDF with the wide margin on the left of every page puts the text of every even page too close to the binding.
Why it grows with page count
A thick book doesn't open flat: the pages curve into the spine, and the curve hides more of each page as the book gets thicker. That is why KDP's minimum gutter grows from 0.375 in to 0.875 in while the outside minimum stays at 0.25 in.
In Microsoft Word, the "Gutter" setting is added on top of the inside margin. KDP's numbers are the total distance from the binding edge to the text, so check the sum, not either setting alone.
Example: a 320-page novel
A 320-page novel needs an inside margin of at least 0.625 in. At 5.5 × 8.5 in with 0.5 in outside margins, the text block is at most 5.5 − 0.625 − 0.5 = 4.375 in wide.
Page count thresholds matter late in a project: if edits take a book from 300 to 302 pages, the minimum gutter jumps from 0.5 in to 0.625 in and every page has to be re-flowed.
Common mistakes
- Using the same margins on left and right pages instead of mirroring them.
- Setting the gutter for the draft page count and not re-checking the final one. Crossing 150, 300, 500 and 700 pages raises the minimum.
- Counting Word's gutter setting twice, or leaving it at zero with an inside margin under KDP's minimum.
- Placing page numbers or running heads close to the binding edge. They must respect the margins too.
- Running important art across the middle of a two-page spread. The center of the spread disappears into the fold.
In kdpbook: kdpbook applies KDP's gutter table by code, from the book's final page count.