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KDP interior calculator
Every number your interior file needs — PDF page size, minimum gutter for your page count, outside margins, and bleed — plus the exact Word settings to apply them. Same specs our production pipeline typesets to.
Want the full margins, gutter & bleed explainer? →
PDF page size
6″ × 9″
152.4 mm × 228.6 mm — exact trim, no bleed
Minimum gutter
0.5″
12.7 mm — inside margin at 300 pages
Minimum outside
0.25″
6.3 mm— top, bottom & outer edges
Recommended working margins (comfortable, not just legal):
Top & bottom 0.75″ · outside 0.5″ · gutter 0.5″. In Word: Layout → Margins → Custom Margins → set Multiple pages: Mirror margins, enter top / bottom / outside, put 0.5″ in the Gutter field, and set the paper size to 6″ × 9″ under Layout → Size.
Or never touch a margin field.
publish.ai typesets your manuscript to these exact specs automatically — gutter sized to your final page count, print-ready PDF at the correct trim — plus a validated EPUB, designed covers, Amazon listing copy, and launch graphics. One upload, minutes, from $29.99.
The three moving parts of interior setup
Page size. Your PDF must be exactly the trim size you choose in KDP — or exactly trim-plus-bleed if ink runs to the edge. A mismatch is the single most common interior rejection: a 6×9 book exported at US Letter, or a with-bleed file uploaded for a no-bleed setup.
Gutter.The binding eats into the inside edge, and thicker books curve more — so KDP’s minimum inside margin steps up with page count: 0.375″ up to 150 pages, 0.5″ to 300, 0.625″ to 500, 0.75″ to 700, and 0.875″ beyond. A book that grows past a threshold during revisions needs its margins re-checked.
Bleed.Trimming isn’t perfectly precise, so anything meant to reach the page edge must be printed 0.125″ past it. Bleed applies to the top, bottom, and outside edges only — never the gutter side, which is bound rather than trimmed.
Once the interior is locked, the page count drives everything on the outside of the book too: spine width, cover dimensions, and printing cost. Compute the interior first, then the cover.
Common questions
What margins does my KDP book need?＋
Three numbers: an inside (gutter) margin that grows with page count — from 0.375″ under 151 pages up to 0.875″ over 700 — plus at least 0.25″ on the top, bottom, and outside edges (0.375″ if your file has bleed). The calculator above gives you all three for your exact book, plus a more comfortable working set that reads like a traditionally published page.
What size should my interior PDF be?＋
Exactly your trim size for a no-bleed (text-only) book — a 6″ × 9″ book uploads as a 6″ × 9″ PDF. If images or backgrounds run to the page edge, add KDP's 0.125″ bleed: the file becomes (width + 0.125″) × (height + 0.25″), so 6.125″ × 9.25″ for a 6×9 book.
Do I need bleed for my book?＋
Only if something printed is meant to reach the very edge of the page — full-page images, chapter-opener art, colored backgrounds. Text-only interiors should be exported at the plain trim size with no bleed; adding bleed to a text book just invites sizing errors.
How do I set these margins in Microsoft Word?＋
Layout → Margins → Custom Margins, set 'Multiple pages' to Mirror margins, enter your top, bottom, and outside values, and put the gutter value in the dedicated Gutter field with Gutter position: Left. Then set the page itself to your trim size under Layout → Size. Word applies the gutter to the binding edge of every page automatically.
Why did KDP reject my interior file?＋
The usual suspects: text or page numbers inside the margin minimums, a gutter that's too small for the final page count (the minimum steps up at 151, 301, 501, and 701 pages), or a PDF exported at the wrong page size — US Letter instead of the trim, or a with-bleed size uploaded for a no-bleed setup.
Is this the same as the KDP cover calculator?＋
No — this page sets up the interior file (the pages inside the book). The cover is a separate single-sheet file with its own math: spine width, wrap, and bleed. Use our KDP cover calculator for that once your page count is final.
Related tools: the full margins, gutter & bleed guide, pick a size with the KDP trim size calculator, estimate pages with the book page count calculator, then build the cover with the KDP cover calculator.