How to Format a Book for Amazon KDP in 2026Interior Formatting Guide: Print and eBook

Why Interior Formatting Matters More Than Most Authors Realise

A poorly formatted book does not just look bad on screen. Formatting errors appear in the printed book as irregular spacing, inconsistent headers, incorrect page numbering and misaligned chapter openings. These errors are invisible during the draft stage, invisible in KDP's digital proof preview, and fully visible the moment someone holds the physical book.

The most common reader feedback for self-published books with formatting issues: "unprofessional," "hard to read," "clearly self-published." These judgments happen before the reader has processed a single idea in the book. Proper formatting is the invisible infrastructure that allows the writing to do its job.

Print Interior: File Requirements

Format: PDF with all fonts embedded. A PDF with fonts not embedded will fail KDP's automated file check or print with font substitutions.

Images: 300 DPI minimum for all images. Images below 300 DPI will print with visible pixelation. For colour interiors, images should be in CMYK colour mode; for black and white interiors, greyscale.

Bleed: If your interior has images or elements that extend to the edge of the page, you need 0.125 inch (3.2mm) bleed on all four sides. Text-only interiors do not require bleed.

Page size: The PDF page size must exactly match your chosen trim size plus bleed margins if applicable. A 6x9 trim with bleed requires a PDF canvas of 6.25 x 9.25 inches.

Trim Sizes: Choosing the Right One

The trim size is the physical dimensions of the finished printed book. KDP supports many sizes. The most commonly used are:

6 x 9 inches: Standard trade paperback. Works for most non-fiction, business, self-help, memoir and literary fiction. The most commonly expected size for adult non-fiction in particular.

5.5 x 8.5 inches: Slightly smaller trade paperback. Common for shorter non-fiction, poetry collections and some literary fiction.

5 x 8 inches: Compact paperback format. Common for mass-market fiction.

8.5 x 8.5 inches: Square format common for children's picture books and illustrated non-fiction.

Your trim size choice affects minimum and maximum page counts, margin requirements and pricing. Confirm the trim size before beginning formatting, as changing it later requires reformatting the entire interior.

Margins: The Specifications That Matter

KDP minimum margin requirements vary by trim size and page count. For a standard 6x9 trade paperback with 150 to 300 pages: inside margin 0.75 inch, outside margin 0.5 inch, top margin 0.75 inch, bottom margin 0.75 inch. The inside margin (gutter) increases with page count to prevent text from disappearing into the spine binding:

24 to 150 pages: 0.375 inch minimum gutter. 151 to 300 pages: 0.75 inch. 301 to 500 pages: 0.875 inch. 501 to 700 pages: 1 inch. 701 or more pages: 1.125 inches.

These are minimums. For comfortable reading, professional formatters typically use slightly larger margins than the minimum, particularly for long-form non-fiction where wider margins improve the reading experience significantly.

eBook Interior: EPUB Requirements

For Kindle, EPUB is the preferred format. KDP also accepts MOBI (older Kindle format), DOCX and HTML, but EPUB produces the most consistent and predictable output across all Kindle devices and apps.

A properly structured EPUB requires: a valid NCX or nav document providing the table of contents, semantic HTML with correct heading hierarchy (h1 for book title, h2 for chapter titles, h3 for section headings), embedded fonts if using custom typography, and a valid OPF file with correct metadata including title, author and language.

Fixed-layout EPUBs for children's picture books and illustrated titles have additional requirements. See children's book publishing services for the specific specifications.

Common Errors That Cause File Rejection

Missing font embedding causes the most file rejections. Every font used in the manuscript must be embedded in the PDF. Fonts not licensed for embedding cannot be used in submitted files.

Incorrect page dimensions cause the second most rejections. The PDF canvas must match the trim size exactly (plus bleed margins if applicable). A PDF produced for A4 paper submitted for a 6x9 trim will be rejected.

Low-resolution images. KDP's automated checker flags any image below 200 DPI. Images between 200 and 300 DPI may pass the check but print with visible quality degradation.

Professional Formatting vs DIY Software

Dedicated book formatting software like Vellum (Mac only) and Atticus (Windows and Mac) produces significantly more reliable KDP-compliant files than Word. Both tools export properly structured EPUB files and print-ready PDFs with correct margin handling. The one-time cost ($50 to $200) is worthwhile for authors publishing multiple titles. For a single title, professional formatting by an experienced formatter is often more cost-effective than learning new software. See full publishing service for formatting included in every package.

For the complete KDP platform setup guide including categories, keywords and pricing, see the Amazon self-publishing guide. For KDP and IngramSpark used together, see print on demand distribution.

Frequently Asked Questions