What margins should your paperback have? It depends on your page count
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R. S. Breed Founder
"Text outside the margins" and "insufficient gutter" are two of the most common reasons KDP bounces an interior. The catch is that the inside margin (the gutter, next to the spine) has to grow as the book gets thicker, because more of each page disappears into the binding.
KDP's minimum inside margin, for example:
- up to 150 pages: 0.375 in
- 151 to 300: 0.5 in
- 301 to 500: 0.625 in
- 501 to 700: 0.75 in
- over 700: 0.875 in
Outside, top and bottom: at least 0.25 in, or 0.375 in if your pages have bleed.
The margin calculator works it out for your book: https://bervet.com/tools/book-margin-calculator
Enter your trim size and page count, tick where you're printing, and you get the page size (with and without bleed) and the margins for each platform, plus one setup that works for all of them. It's clear about which numbers are rules and which are suggestions: KDP publishes minimums, IngramSpark, Lulu and Barnes & Noble Press publish recommendations, and Bookvault and Draft2Digital Print don't publish margins at all.
Tip: set the margins for the page count you'll end up with, not the one you have now. If edits take you from 290 to 310 pages, KDP's minimum goes up.
No account needed.