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Best Book Size for Amazon KDP and Trim Sizes to Use

Best Book Size for Amazon KDP: Proven Trim Sizes That Sell for Fiction, Nonfiction, and Journals

Estimated reading time: 5 minutes

  • Match trim size to genre expectations—6″ x 9″ is a safe default for many nonfiction titles and plenty of fiction.
  • Trim size influences page count, print cost, readability, and thumbnail/shelf presence—choose size based on text, images, or worksheets.
  • Use production tools that handle covers and EPUB conversion to speed delivery and reduce formatting errors.

Table of contents

Why trim size matters: printing, price, and reader expectations

Choosing the best book size for Amazon KDP is more than aesthetics. The trim size you pick changes how many pages your manuscript becomes, how easy the book is to read, how it looks in thumbnails, and how much it costs to print.

In the US market, 6" x 9" is the most common and economical choice for many titles because it balances readability, portability, and cost. That makes it a strong default for first-time self-publishers and for authors who publish at scale.

Practical effects of trim size

Page count: Smaller trims increase page count for the same word count; larger trims reduce page count. Amazon KDP enforces minimum and maximum page counts depending on format and trim.

Printing cost: Larger trim sizes and more pages both raise printing costs and reduce per-unit royalty.

Reader expectations: Genre readers expect certain formats — a trade paperback feels different than a business paperback.

Visual content: Diagrams, photos, or wide tables often require 7″ x 10″ or larger to remain legible.

Practical constraints from Amazon KDP

Amazon KDP sets page minimums and maximums that interact with trim choice. Many hardcover trims require at least 75 pages and cap at about 550 pages; paperbacks can accept between 24 and 828 pages depending on trim and interior options.

These limits mean you must plan manuscript length and trim together — switching trim sizes late in production can push a book over or under KDP limits.

If you’re preparing files for KDP and want a straightforward reference for margins, bleed, and technical settings, check the Amazon KDP Formatting Guide 2 for exact specs and recommended workflows.

Below are proven trim sizes that sell, organized by common categories. Use these as a starting point — your content should drive the final choice.

Best choices: 5″ x 8″, 5.25″ x 8″, 5.5″ x 8.5″, 6″ x 9″.

Why: Fiction readers prioritize portability and long reading comfort. Smaller trims feel like mass-market paperbacks; 6″ x 9″ is a neutral, widely accepted option.

Best choice: 6″ x 9″. Alternatives: 5.5″ x 8.5″ for compact guides; 7″ x 10″ for workbooks with charts.

Why: Nonfiction often contains longer paragraphs, sidebars, or numbered lists. 6″ x 9″ gives comfortable line length and looks professional on retailer pages.

Best choices: 7″ x 10″, 8″ x 10″, 8.5″ x 11″.

Why: Larger pages allow diagrams, tables, and code snippets to remain legible without cramping.

Best choices: 8″ x 8″, 8.5″ x 8.5″, 8.5″ x 11″.

Why: These genres rely on full-bleed artwork; choose a size that preserves artwork resolution.

Best choices: 6″ x 9″, 6.14″ x 9.21″ (trade sizes), 7″ x 10″.

Why: Daily-use formats need a balance of portability and usable writing space; 6″ x 9″ is familiar and cheap to produce.

Best choices: 8.5″ x 11″, 8.25″ x 11″.

Why: Food photography and recipes benefit from wider layouts; expect higher printing costs and plan royalties accordingly.

  • Compact & portable: 5″ x 8″, 5.25″ x 8″
  • Standard trade: 6″ x 9″
  • Photo/illustration rich: 8″ x 10″, 8.5″ x 11″
  • Square art/picture books: 8″ x 8″, 8.5″ x 8.5″

How to choose and produce your final trim

A simple, repeatable process helps you pick the best book size and then produce correct files for Amazon KDP without unexpected rework.

1. Match genre and reader expectations

Start by looking at top-selling books in your exact niche. If most bestsellers are 6″ x 9″, matching that standard reduces friction and signals professionalism.

2. Consider content type and layout

Text-only: smaller trims are fine. Heavy diagrams or sidebars: choose larger formats to avoid tiny type. Mixed content: 6″ x 9″ often suffices, but check sample pages.

3. Estimate page count and check KDP limits

Use industry averages — roughly 250–300 words per page for 6″ x 9″ with standard margins and 12-point body text — to estimate pages. If your estimated page count approaches KDP maximums, consider a larger trim or reduce content.

4. Factor printing costs and pricing strategy

Bigger pages plus higher page count raise print cost, which affects list price and final royalty. If you need a paperback under $10, smaller trims and thin paper can keep costs down.

5. Proof internally and in print

Export a PDF proof with correct trim and bleed settings, then order a printed proof from KDP. Confirm margins, gutter, and image rendering; don’t rely on the screen alone.

6. Use production tools that simplify the final steps

Creating covers that read well at thumbnail size and producing EPUBs for Kindle and other stores are common stumbling points late in production. A one-click approach to cover design speeds work when you need market-ready art quickly.

For covers, consider a tested cover generator that produces full front covers with readable typography and proper hierarchy. For converting interiors to ebooks, an automated EPUB converter can embed the cover, add metadata, and create clean chapter navigation so files preview correctly across stores.

7. Check technical formatting and margins

Margins, bleeds, and gutter settings differ by trim and interior option. For exact pixel/point values and recommended margins for popular trims, consult a technical reference like the Amazon KDP Formatting Guide 2.

8. Finalize and upload

Once you have a printed proof you’re happy with, finalize metadata (including ISBN where relevant), the interior, and the cover. If you need help with bulk distribution or uploading to multiple retailers, tools that specialize in uploading to retailers can simplify the process.

If you want a single system that generates, humanizes, formats, and produces final files for KDP and beyond, BookAutoAI provides book generation and formatting services for nonfiction authors.

Design details that affect reader experience

Typography: Line length matters — too wide on large trims makes long lines hard to read; too narrow increases hyphenation. 6″ x 9″ pairs well with 10–12 point body text depending on font.

Margins and gutter: Ensure the inner gutter provides room for binding; KDP proofs expose creep/binding differences that vary with page count and trim.

Thumbnail clarity: Most readers first see a small thumbnail on retailer pages. Strong title typography and an uncluttered cover background perform better than ornate artwork that reads poorly when scaled down.

Wrap-up

Picking the best book size for Amazon KDP balances reader expectations, content type, printing costs, and KDP technical constraints. Start with genre norms, test with a printed proof, and use tools that reduce formatting friction so you can focus on content rather than file errors.

For non-fiction authors who need a fast, reliable pipeline from manuscript to store-ready files, BookAutoAI is positioned to generate, humanize, format, and produce finished books at scale.

FAQ

Is 6" x 9" always the best book size for Amazon KDP?

No single size is always best, but 6″ x 9″ is a reliable default for many nonfiction and fiction books. Choose a different size when photos, diagrams, or worksheets require more space.

How does trim size affect my KDP royalties?

Trim size affects printing cost and page count, which are used to calculate print cost and thus royalty. Larger trims and heavier paper increase print cost and may require higher list prices.

I have a lot of images—should I use bleed?

Yes. For images that run to the edge, set up full-bleed pages with the correct bleed margin for your chosen trim. Consult a formatting guide for exact values.

Can I change my trim size after publishing?

Yes, but changing trim size requires reformatting interior and cover files and re-uploading. If you change trim, check page count, ISBN, and price for consistency.

What file types should I upload for the interior and cover?

KDP accepts print-ready PDF files for interiors and PDF or JPG for covers depending on workflow. For ebooks, EPUB is standard; a clean EPUB previews correctly across stores.

How can I make this process faster and less error-prone?

Use tools that automate document formatting, create professional covers, and output store-ready EPUB files. That reduces the usual trial-and-error and speeds publishing.

Sources

Best Book Size for Amazon KDP: Proven Trim Sizes That Sell for Fiction, Nonfiction, and Journals Estimated reading time: 5 minutes Match trim size to genre expectations—6″ x 9″ is a safe default for many nonfiction titles and plenty of fiction. Trim size influences page count, print cost, readability, and thumbnail/shelf presence—choose size based on…