Short answer. KDP lists 16 paperback trim sizes for Amazon.com, from 5.06 x 7.81 to 8.5 x 11 inches, plus a custom size. Five are regular and eleven are large, which cost more to print. Most novels fit 5 x 8 to 5.5 x 8.5, memoirs 5.5 x 8.5 or 6 x 9, and how-to and business books usually 6 x 9.
Key points
- 6 x 9 is the default in KDP's setup screen and the most common US trim size, per KDP.
- A size wider than 6.12 inches or taller than 9 inches is "large" and prints at a higher per-page cost.
- Pick the size before formatting. Margins, page count and spine width all follow from it.
- Our paperback interior formatting starts with the trim size you choose, then sets every page to it.
What are the KDP paperback trim sizes?
KDP's help page lists these for Amazon.com:
Regular (5 sizes): 5 x 8, 5.06 x 7.81, 5.25 x 8, 5.5 x 8.5, 6 x 9.
Large (11 sizes): 6.14 x 9.21, 6.69 x 9.61, 7 x 10, 7.44 x 9.69, 7.5 x 9.25, 8 x 10, 8.25 x 6, 8.25 x 8.25, 8.5 x 8.5, 8.5 x 11, 8.27 x 11.69.
You can also type in a custom size. The width has to sit between 4 and 8.5 inches and the height between 6 and 11.69 inches.
Which trim size costs more to print?
The large ones. On Amazon.com a black ink book over 110 pages costs $1.00 plus $0.012 a page at a regular size, and $1.00 plus $0.017 a page at a large size. For a 300-page book that is $4.60 against $6.10, a gap of $1.50 on every copy you sell. Our post on KDP paperback print cost by page count works through more examples.
Which trim size suits fiction, memoir and non-fiction?
KDP's own advice is to find books like yours and copy what readers expect. Our starting point for each kind of book:
- Novels: 5 x 8, 5.25 x 8 or 5.5 x 8.5. They feel like a bookstore paperback.
- Memoir and narrative non-fiction: 5.5 x 8.5 or 6 x 9.
- How-to, business and self-help: 6 x 9.
Those pairings are our judgement from bookstore conventions, not a KDP rule. Pull three books from your genre off a shelf and measure them before you decide.
How does the trim size change your page count?
A smaller page holds fewer words, so the book gets longer. Our sample book shows the scale of the change. On 13 Oct 2026 we checked it with pdfinfo: our sample manuscript was a Word file of 12 Letter-size pages, and the formatted interior is 14 pages at 6 x 9 (432 x 648 points). The body pages held 379 words on average.
At that rate an 80,000-word novel runs about 210 pages at 6 x 9. At 5 x 8 it runs longer, which raises the print cost and widens the spine.
Where we come in: you pick the trim size, and we set every page, margin and gutter to it and check the PDF against KDP's print specs. Send us a chapter and we format it as a free sample.
Can you change the trim size after publishing?
No, not on the same book. KDP locks the trim size once a paperback is published. To change it you publish a new edition, which needs its own ISBN, and a cover wrap resized to the new trim. That is why the choice belongs at the start, before a single margin is set.
Does the trim size change your margins?
No. KDP's minimum margins depend on page count and bleed, not on trim size. Our post on KDP margins by page count has the full table. If your book has pictures that reach the page edge, read KDP bleed vs no bleed as well, because bleed adds 0.125 inch to the width and 0.25 inch to the height of the page.
What else do authors ask about KDP paperback trim sizes?
6 x 9 inches, according to KDP. It is the default in the Print Options section.
No. Large means wider than 6.12 inches or taller than 9 inches.
In the standard list, 5.06 x 7.81 is the shortest and 5 x 8 the narrowest. A custom size can go down to 4 x 6.
You can, but it prints at the large-size rate and few novels use it.
No. KDP hardcovers come in five sizes only, from 5.5 x 8.5 to 8.25 x 11.
What should you do next?
Measure three books from your genre and pick the size they share. Then set your page to that size before anything else. A paperback we format can also be reset as a hardcover interior at one of KDP's five hardcover sizes. If you want the interior done for you, start on our paperback interior formatting page.
