Guide

KDP gutter and margins by page count

KDP's inside margin, often called the gutter, grows with the page count because a thicker book curves more into its spine. Outside, top and bottom margins have one fixed minimum. Here is the whole table and how to apply it.

KDP's minimum margins for a paperback interior (from KDP's help page, checked 11 October 2026)
Page count	Inside (gutter) margin	Outside, top, bottom: no bleed	Outside, top, bottom: with bleed
24 to 150	0.375 in (9.6 mm)	0.25 in (6.4 mm)	0.375 in (9.6 mm)
151 to 300	0.5 in (12.7 mm)	0.25 in (6.4 mm)	0.375 in (9.6 mm)
301 to 500	0.625 in (15.9 mm)	0.25 in (6.4 mm)	0.375 in (9.6 mm)
501 to 700	0.75 in (19.1 mm)	0.25 in (6.4 mm)	0.375 in (9.6 mm)
701 to 828	0.875 in (22.3 mm)	0.25 in (6.4 mm)	0.375 in (9.6 mm)

Source: KDP Help, Set Trim Size, Bleed, and Margins. These are minimums. KDP's Print Previewer flags anything inside them.

The inside margin is the one next to the spine. On a right-hand (odd) page it is the left margin; on a left-hand (even) page it is the right margin. That is why Word needs "Mirror margins".

What "inside margin" means here

KDP's inside number is the full distance from the spine edge of the page to your text. It already includes any gutter. If your layout program has a separate gutter setting (Word does), the inside margin plus the gutter must reach the number in the table.

Word: Layout > Margins > Custom Margins, Multiple pages: Mirror margins. Inside + Gutter = KDP's inside margin.
Bleed only changes the outside, top and bottom minimums (0.375 in instead of 0.25 in). The inside minimum is the same either way.

Page size with bleed

Choose bleed only if images or backgrounds must run off the edge of the page. With bleed, the PDF page is larger than the trim: width + 0.125 in, height + 0.25 in. A 6 x 9 in book with bleed uses 6.125 x 9.25 in pages. Without bleed the PDF page is exactly the trim size. Novels and most nonfiction don't need bleed.

Worked examples

Minimums for three real-world cases (no bleed)
Book	Inside	Outside, top, bottom	Note
Poetry collection, 96 pages, 5 x 8 in	0.375 in	0.25 in	First band
Novel, 284 pages, 5.5 x 8.5 in	0.5 in	0.25 in	Close to 300: if edits push it past, it needs 0.625 in
Fantasy novel, 512 pages, 6 x 9 in	0.75 in	0.25 in	501 to 700 band

Minimum isn't the same as comfortable

The table is the line KDP's checker enforces. Pages set exactly at 0.25 in outside look cramped in the hand, and text close to the spine is hard to read in a thick book. The four interior designs in Bookcut use 0.75 to 0.8 in inside and 0.6 to 0.65 in outside before any KDP adjustment, and the inside margin is raised whenever a book's page count needs more.

Three things that catch people out

The page count moves when you change the margins. Bigger margins mean fewer words per page and more pages, which can push the book into the next band. Recheck the page count of the final PDF.
KDP rounds odd page counts up. A 151-page file is printed as 152 pages, and both are in the 151 to 300 band.
The 828-page ceiling is for white paper. On cream paper the regular trim sizes stop at 776 pages.

Or let Bookcut do the setup

Bookcut reads the .docx you wrote the book in, finds the chapters and front matter, and typesets every page at your trim size with KDP's margin table for your page count already applied. You can look at every page free, and download your first chapter as a PDF to print at home (it has a light "Preview" watermark). When it looks right, the clean print PDF and an EPUB are $12, once for that book. It runs in your browser; the manuscript isn't uploaded.

Open Bookcut