KDP Trim Size Picker
Answer 4 quick questions and get a recommended Amazon KDP book size — with reasons, a comparison table, and links to related calculators.
What type of book are you making?
This helps narrow down the best sizes for your genre.
How to Choose the Right Trim Size
Match Your Genre
Readers expect certain sizes. Fiction readers prefer 5.5"×8.5" or 6"×9". Children's books need larger, often square formats. Cookbooks work best at 8"×10" or larger.
Consider Print Cost
Smaller trims mean more pages (higher print cost). Larger trims fit more per page but require more cover area. 6"×9" is the best balance of readability and cost.
Check Hardcover Availability
Only 6 of 17 paperback sizes are available in KDP hardcover. If you plan to offer both, pick a size that works for both formats.
Frequently Asked Questions
What is the most popular KDP trim size?+
6"×9" is the most popular trim size for trade paperbacks on Amazon. It works well for nonfiction, self-help, business books, and general fiction. 5.5"×8.5" is the second most popular, preferred for mass-market-style fiction and memoirs.
What trim size should I use for a children’s book?+
Most children’s picture books use 8.5"×8.5" (square) or 8"×10" (portrait). For chapter books (ages 7–12), 5.5"×8.5" or 6"×9" work well. KDP only supports landscape orientation for hardcover, not paperback.
Can I change my trim size after publishing?+
You can change your trim size by creating a new edition, but this generates a new ISBN and your existing reviews will not carry over. Choose your trim size carefully before publishing. You can always unpublish and republish, but you lose review history.
What trim sizes does KDP support for hardcover?+
KDP case-laminate hardcover supports 6 sizes: 5.5"×8.5", 6"×9", 6.14"×9.21", 6.69"×9.61", 7"×10", and 8.25"×11". The most common choices are 6"×9" and 5.5"×8.5".
Found your trim size? Build the book
KDP Builder takes you from this free tool to a complete, upload-ready package — manuscript or interior, cover, and metadata.
More Free KDP Tools
Keep prepping your book — every tool below is free and needs no signup.
KDP Cover Size Calculator
Full wrap-cover dimensions — width, height, spine and bleed for any trim size.
Spine Width Calculator
Exact spine width using Amazon's official paperback and hardcover formulas.
Print Cost Calculator
Exact KDP printing costs and profit margins for any page count, ink type, and binding.
Page Count Calculator
Convert word count to pages for any trim size, font, and line spacing.
Related KDP Guides
Step-by-step formatting guides that pair with this tool.
Ready to Build the Whole Book?
Take it further with a complete, Amazon-ready project in KDP Builder.