KDP Trim Sizes Explained — Which to Choose for Your Book
KDP trim sizes are the finished dimensions of your printed book, measured in width by height (inches). Amazon KDP offers over 30 trim size options for paperbacks and hardcovers, but most self-published authors only need to consider about five or six. The trim size you pick affects your page count, printing cost, royalty, and how your book looks next to competitors on a shelf or in a thumbnail.
Every KDP Trim Size Available Right Now
KDP supports trim sizes from 5" x 8" all the way up to 8.5" x 11". Here are the ones you'll actually encounter, grouped by use case:
Popular for fiction and general nonfiction:
- 5" x 8"
- 5.25" x 8"
- 5.5" x 8.5"
- 6" x 9"
Popular for workbooks, journals, and coloring books:
- 8" x 10"
- 8.5" x 8.5"
- 8.5" x 11"
Less common but still available:
- 5" x 5" (square, hardcover only in some markets)
- 6.14" x 9.21" (matches some traditional publishing standards)
- 7" x 10" (textbooks and technical manuals)
The full list is on KDP's help pages, but honestly, about 80% of self-published paperbacks use one of four sizes: 5" x 8", 5.5" x 8.5", 6" x 9", or 8.5" x 11". Everything else is niche.
How to Pick the Right Trim Size for Your Genre
Genre expectations matter more than personal preference here. Readers have unconscious expectations about how a book should feel in their hands. Go against those expectations, and your book feels "off" even if nobody can explain why.
Romance, thriller, mystery, literary fiction: 5" x 8" or 5.25" x 8". These are the standard mass-market and trade sizes. Pick up any novel from a Big Five publisher and you'll likely find one of these. If your book is under 300 pages, 5" x 8" keeps the spine thick enough to look substantial.
Self-help, business, general nonfiction: 5.5" x 8.5" or 6" x 9". The slightly larger format gives you room for pull quotes, sidebars, or diagrams without cramming everything together. 6" x 9" is the go-to for nonfiction authors who want their book to look authoritative.
Children's books: 8.5" x 8.5" or 8" x 10". You need space for illustrations. Square formats work well for picture books aimed at younger kids.
Workbooks, planners, journals, coloring books: 8.5" x 11". This matches standard US letter size, which means users can easily photocopy pages or lay the book flat on a desk.
Poetry: 5" x 8" or 5.5" x 8.5". Smaller formats feel intimate, which suits the genre. A 6" x 9" poetry collection with short poems looks like it has too much white space on every page.
Trim Size Affects Your Printing Cost and Royalties
This is where authors often get surprised. A larger trim size doesn't always mean higher printing costs, because a larger page fits more words, which means fewer total pages.
Here's a concrete example. A 60,000-word novel formatted at 5" x 8" with standard margins and 11pt font might run about 280 pages. The same manuscript at 6" x 9" could drop to around 210 pages. KDP charges per page for printing, so fewer pages means a lower print cost and a higher royalty per sale.
But don't just chase the lowest page count. A novel at 6" x 9" with only 210 pages looks thin. The spine will be narrow, and the cover won't show much text in thumbnail view. A 5" x 8" version of the same book has a thicker spine, more visual presence, and meets reader expectations for fiction.
The sweet spot is choosing the trim size your genre expects, then adjusting font size, line spacing, and margins to land in a reasonable page count. For fiction, aim for at least 200 pages. For nonfiction, 150+ is fine.
Hardcover Trim Sizes on KDP
KDP's hardcover options have a smaller set of available trim sizes compared to paperback. As of now, you get these choices for case laminate hardcovers:
- 5.5" x 8.5"
- 6" x 9"
- 6.14" x 9.21"
- 7" x 10"
- 8.5" x 11"
If you're publishing both paperback and hardcover editions, pick a trim size that's available in both formats. 5.5" x 8.5" and 6" x 9" are the safest bets. Using the same trim size for both editions means you can reuse your interior file without reformatting.
Common Trim Size Mistakes to Avoid
Picking a size because you like it personally. Your preference doesn't matter as much as what your target reader expects. Browse the top 20 bestsellers in your category and check their product details. Amazon lists the print dimensions. That's your benchmark.
Ignoring bleed requirements. If your book has images, graphics, or color that extends to the edge of the page, you need bleed. Bleed adds 0.125" to each side of the trim, which changes your PDF dimensions. A 6" x 9" book with bleed needs a PDF that's 6.25" x 9.25". Set this up before you start formatting, not after.
Switching trim size after your cover is designed. Your cover template depends on page count and trim size. Change either one, and you need a new cover file. Finalize your interior first, confirm the page count, then order the cover.
Forgetting about the listing. Your trim size, page count, and interior formatting are only half the equation. The other half is how your book appears on Amazon's product page. Your title, subtitle, description, and keywords need to be just as polished as your interior. PublishRank's Listing Optimizer can help you audit and improve those elements so your well-formatted book actually gets found and clicked.
Quick Reference: Most Common Choices by Book Type
| Book Type | Best Trim Size | Why |
|---|---|---|
| Novel (any genre) | 5" x 8" or 5.25" x 8" | Matches trade paperback standards, feels right in hand |
| Self-help / Business | 5.5" x 8.5" or 6" x 9" | Room for formatting variety, looks professional |
| Workbook / Journal | 8.5" x 11" | Standard letter size, easy to write in |
| Children's Picture Book | 8.5" x 8.5" or 8" x 10" | Large format for full-page illustrations |
| Poetry | 5" x 8" | Compact, intimate format suits the genre |
| Cookbook / Art Book | 8" x 10" or 8.5" x 11" | Space for photos and visual layouts |
Frequently Asked Questions
What is the most popular KDP trim size?
6" x 9" is the single most used trim size across all KDP categories because it works for both fiction and nonfiction. That said, for novels specifically, 5" x 8" and 5.25" x 8" are more common and better match reader expectations for trade paperbacks.
Can I change my KDP trim size after publishing?
Yes, but it's a pain. You'll need to reformat your entire interior PDF and get a new cover template, since the spine width and cover dimensions are calculated from your trim size and page count. Amazon treats it as an update to the existing listing, not a new book, so your reviews stay intact. But expect your book to be temporarily unavailable during the review process.
Does trim size affect KDP printing cost?
Not directly. KDP calculates printing cost based on page count, ink type (black or color), and marketplace. However, trim size affects page count indirectly. A larger trim size fits more words per page, reducing total pages and lowering the per-unit print cost. So yes, your trim size choice can change your royalty by a meaningful amount.
What trim size should I use for a KDP journal or notebook?
8.5" x 11" is the standard for journals, notebooks, and planners because it matches US letter paper. If you want a more portable journal, 6" x 9" is a good alternative. Both sizes are widely used in the low-content book space.
Are KDP trim sizes measured in inches or centimeters?
KDP lists trim sizes in inches. If you're formatting in a program that uses millimeters or centimeters, you'll need to convert. For example, 6" x 9" equals 152.4mm x 228.6mm. Double-check your document setup before exporting to PDF, because even a fraction of an inch off will get your file rejected.