Home › Blog › KDP margins, bleed and spine
Amazon publishes these numbers but never explains them. Here is what each one means, where it comes from, and which three get people rejected.
The gutter is the inside margin — the one against the binding. It is larger than the outer margin because a thicker book curves more sharply at the spine, swallowing more of the page. A 600-page book physically cannot be opened flat, so Amazon demands more clearance.
| Page count | Minimum gutter |
|---|---|
| 24 – 150 | 0.375" |
| 151 – 300 | 0.5" |
| 301 – 500 | 0.625" |
| 501 – 700 | 0.75" |
| 701 – 828 | 0.875" |
Two consequences people miss. First, these are tiers: adding one puzzle that pushes you from 150 to 151 pages increases your required gutter by an eighth of an inch across the entire book. Second, the gutter alternates — left on odd pages, right on even pages — because odd pages are right-hand pages. Software that applies a fixed left margin to every page produces a book where every second page runs into the spine.
Top, bottom and the outside edge need at least 0.25" without bleed, or 0.375" with bleed. Anything closer risks being trimmed off, because guillotines have tolerance.
This is also why page numbers cause trouble: designers place them a comfortable-looking distance from the edge and end up inside the danger zone. Keep any live element — text, page numbers, rules — at least a quarter inch from the trim line.
Bleed is extra artwork extending beyond the trim line, so that when the trimmer cuts slightly off-centre there is no white sliver at the edge.
Amazon does not tell you your spine width. You calculate it:
| Paper & ink | Inches per page |
|---|---|
| Black ink, white paper | 0.002252 |
| Black ink, cream paper | 0.0025 |
| Premium colour, white paper | 0.002347 |
Multiply by your final page count. A 120-page book on white paper: 120 × 0.002252 = 0.2702". On cream, the same book has a 0.3" spine — cream stock is thicker, and switching paper after you've made the cover is a classic self-inflicted rejection.
So a 6×9 book of 120 pages on white paper needs a cover exactly 12.520" × 9.250", or 3756 × 2775 pixels at 300 DPI.
KDP only prints text on the spine for books with more than 79 pages. Below that the spine is too narrow: binding drift of up to 0.0625" would pull your title round onto the front or back cover.
A related trick worth knowing — on any thin book, make the spine the same colour as the covers. If it's a contrasting colour and the wrap drifts even slightly, you get an obvious off-centre stripe. Matching colour makes drift invisible.
Amazon prints a barcode in a 2" × 1.2" box at the bottom-right of your back cover. Anything you put there — blurb, logo, author photo — gets covered. Leave it empty, and ideally leave it light so the barcode scans reliably.
Our free calculator works out spine width, full cover dimensions and the required gutter for any trim, page count and paper — and hands you a blank template with every zone marked. And in the Studio, all of it is derived from your live book, so the cover cannot drift out of sync with the interior.
Gutter tiers, the interior-versus-cover bleed difference, spine width per paper stock and the page ceilings nobody mentions. I’ll send the guide and a note when Amazon changes the rules.
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