Amazon KDP Book Prep: Spine, Cover and Margins

    1

    KDP-ready interiors and covers on the first try: exact spine/cover math, margins by page count, and fixes for KDP's vague upload errors.

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    Amazon KDP Book Prep: Spine, Cover and Margins

    Example session with this skill installed

    My paperback is 6x9 inches, 320 pages, white paper, no bleed. What are the spine width, full cover size in inches and pixels at 300 dpi, and minimum margins?

    • Read your context and instructions
    • Compiled the amazon kdp book

    Here are the numbers for a 6×9 in paperback, 320 pages, white paper, no bleed. I got them from the skill's kdp_cover.py script.

    Spine width

    • 320 pages × 0.002252 in = 0.7206 in (18.30 mm).
    • Spine text is allowed because the book has more than 79 pages. Keep 0.0625 in clear on each side of the spine.

    Full cover (one PDF, back cover on the left)

    • The width is 0.125 bleed + 6 back + 0.7206 spine + 6 front + 0.125 bleed.
    • Size: 12.9706 × 9.25 in, which is 3891 × 2775 px at 300 dpi.
    • The back panel runs from 0 to 6.125 in. The spine runs from 6.125 to 6.8456 in. The front panel comes after that.
    • Leave about 2 × 1.2 in clear at the bottom right of the back panel. KDP prints the barcode there.
    • The cover always includes bleed, even though your interior has none.

    Minimum interior margins (6 × 9 in pages, no bleed)

    • Inside (gutter): at least 0.625 in, because 301–500 pages falls in that tier.
    • Outside, top and bottom: at least 0.25 in.
    • Headers, footers and page numbers count toward these margins. A footer drawn below the margin fails the previewer, so move it inward rather than shrinking the page.

    If the page count changes, recompute the cover, because the new spine width shifts the front panel. Before you publish, check the cover alignment, the first and last pages, and one page with a table or image in the KDP Previewer.

    Real output from a Claude Code session with this skill installed.

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    About this skill

    Stop wrestling with Amazon KDP's opaque error messages and rejected PDF files. This skill provides the exact technical specifications and mathematical calculations that give your files the best chance to pass KDP's review on the first attempt. It handles the complex geometry of spine widths and margins based on page count and paper type, based on KDP's published specifications.

    What it does

    • Calculate spine math determines the precise spine width and full cover dimensions in inches and pixels.
    • Set margin requirements identifies the mandatory gutter and outside margins based on specific page counts to avoid interior rejection.
    • Format interior PDFs provides specs for font embedding, DPI requirements, and bleed settings to prevent scaling issues.
    • Optimize eBook covers defines the ideal aspect ratios and resolution for Kindle storefront visibility.
    • Troubleshoot upload errors solves the common "fix highlighted errors" loop and barcode placement failures.

    How it works

    1. Input manuscript data including page count, trim size, and paper color (white, cream, or color).
    2. Generate specifications for the cover wrap PDF and interior layout margins.
    3. Validate metadata against KDP rules for titles, keywords, and AI-content disclosures.
    4. Fix rejection errors using targeted advice for vague KDP dashboard warnings.

    Frameworks & tools

    This tool uses a Python-based calculation logic for print geometry and follows Amazon KDP's specific manufacturing requirements for EPUB, PDF, and JPG formats.

    Why this beats prompting it yourself

    Standard LLMs often hallucinate paper thickness constants or use outdated royalty brackets. This skill uses hard-coded constants for white and cream paper stocks, so the spine width and panel positions follow KDP's published per-page thickness.

    Use cases

    • Drafting a 6x9 paperback cover for a 320-page white-paper interior.
    • Troubleshooting why the KDP Previewer flags text outside the margin.
    • Calculating the list price for the 70% royalty band in specific marketplaces.
    • Formatting an HTML-to-PDF conversion that avoids "shrink to fit" scaling errors.

    Known limitations

    Does not perform the actual layout design or file conversion. A human must click the final "Publish" button to bypass KDP's automated click detection.

    Calculation logic only. Does not generate PDF/EPUB files directly. Requires manual final click on KDP dashboard. Spine text requires 79+ pages.

    How to use

    1. 1

      Connect your agent to the Agensi MCP

      Copy the prompt and paste it into Claude, ChatGPT, Cursor or any agent that supports MCP. It sets up the connection for you. Manual setup

    2. 2

      Sign in to Agensi

      Your agent shows a sign-in link. Sign in and click Allow.

    3. 3

      Ask for what you need

      Your agent loads this skill and uses it on your task. It always asks before any payment.

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    Security scan passed 7 days ago

    • Free with an Agensi account

    Requires

    Python 3.8+

    Permissions

    Terminal / Shell
    Listed7 days ago

    What's inside

    Frequently Asked Questions

    The skill handles all KDP-supported paper types including white, cream, and Premium Color, using specific manufacturing constants to ensure your spine width is accurate to the thousandth of an inch.

    While it doesn't edit your files directly, it provides the precise margin, bleed, and dimension coordinates you need to input into tools like Canva, InDesign, or Affinity Publisher to pass inspection.

    It is designed to troubleshoot common "Black Box" errors, such as text outside the margins or incorrect trim sizes, by providing the exact mathematical adjustments needed to satisfy the KDP Print Previewer.

    A SKILL.md with KDP paperback and eBook specs, metadata and royalty rules, AI-disclosure notes and fixes for vague upload errors, plus scripts/kdp_cover.py, which computes spine width, full-cover size and minimum margins. It is free.

    The constants follow KDP's published specifications as of version 1.0. KDP can change them, so check its help pages (paper thickness, margins, cover size) before a print run.

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