How KDP margins work
Every page has four margins, but only two numbers change. The outside, top and bottom margins share one minimum: 0.25 inches, or 0.375 inches if your interior uses bleed. The inside margin, called the gutter, sits against the binding and grows with page count, because a thicker book bends further into its spine when it is opened.
| Page count | Minimum gutter |
|---|---|
| 24 to 150 | 0.375" |
| 151 to 300 | 0.5" |
| 301 to 500 | 0.625" |
| 501 to 700 | 0.75" |
| 701 to 828 | 0.875" |
Left pages and right pages
The gutter swaps sides from page to page. On a right-hand (odd) page the binding is on the left, so the gutter is the left margin. On a left-hand (even) page it is the right margin. The preview draws both pages side by side so you can see the mirror. If you lay out in a word processor, use mirrored margins with the gutter as the inside value.
Bleed changes the page size, not the trim
With bleed on, your PDF pages are 0.125 inches wider (on the outside edge only, never the binding edge) and 0.25 inches taller. A 6 x 9 interior becomes a 6.125 x 9.25 inch PDF. The margins are still measured from the trim line, which the preview shows dashed inside the pink bleed.
These are the same margin rules the Book Studio's KDP compliance report checks. To see how the thickness of the book affects the cover, try the spine width calculator.
Frequently asked questions
What are KDP's minimum margins?
Outside, top and bottom margins must be at least 0.25 inch without bleed or 0.375 inch with bleed. The inside (gutter) margin depends on page count: 0.375 inch up to 150 pages, 0.5 inch for 151 to 300, 0.625 inch for 301 to 500, 0.75 inch for 501 to 700 and 0.875 inch for 701 to 828.
What is the gutter?
The gutter is the inside margin next to the binding. Pages curve into the spine when a book is opened, so text too close to it disappears into the fold. Thicker books curve more, which is why KDP asks for a bigger gutter as page count rises.
Do I need bleed for a puzzle book?
Only if something prints right to the edge of the page, such as a shaded header band or a full-page background. Plain puzzle pages with white borders do not need bleed. Turning bleed on makes the PDF page 0.125 inch wider and 0.25 inch taller and raises the outside margin minimum to 0.375 inch.
Are bigger margins better?
Up to a point. The numbers here are minimums, and many publishers add a little extra so the page does not feel crowded. For puzzle books, though, every fraction of an inch of live area lets a grid print bigger, so staying close to the minimum is common.
Why does KDP reject my interior for margins?
Usually because text or a grid crosses into the gutter or outside margin on some pages, often the answer key or a page with a long word list. KDP checks every page, so one overflowing page is enough to fail review.