Margins and gutter
Inside margin needs more space as page count grows because pages curve into the spine.
KDP formatting guide
A practical checklist for authors preparing a paperback book: trim size, margins, gutter, bleed, images, front matter, back matter, PDF proofing and upload readiness.
Step 1
Trim size is the final physical size of the paperback page after printing and cutting. It affects line length, page count, margins, cover dimensions and reader comfort. Changing trim size late can force you to re-check typography, image placement and page count.
KDP documents trim size, bleed and margin requirements in its help center. Use the official KDP page as the final authority for current upload rules.
KDP trim size, bleed and marginsChecklist
Inside margin needs more space as page count grows because pages curve into the spine.
Use bleed only when content or images must extend to the page edge after trimming.
Check front matter, chapter starts, blank pages and numbering behavior before export.
Confirm images are present, large enough, optimized and placed inside safe areas.
Interior formatting and cover dimensions must agree with trim size, page count and paper choice.
Generate a PDF draft, inspect spreads, and never assume the upload preview will catch everything for you.
InkVault workflow
InkVault is designed to surface practical warnings around paperback page size, margins, gutters, images, cover state, missing structure and PDF tool availability while the book project is still editable. That does not replace KDP validation, but it reduces late surprises.
FAQ
Check trim size, inside gutter, outside margins, bleed, cover state, image resolution, page count, front matter, back matter and the final PDF proof.
No. KDP margin requirements depend on page count and whether the interior uses bleed. The inside margin, also called gutter, increases as page count increases.
No. InkVault can help catch common production issues earlier, but the final acceptance decision belongs to KDP and the publisher should proof every generated file.
Next steps
See the InkVault page focused on paperback and print upload checks.
KDP workflowGo deeper into page geometry for print books.
Read page geometry guideReview the broader layout workflow.
Book layout workflow