Trim size is the physical dimension of your printed book. It determines how your interior looks on the page, how much you can fit per page, and — because printing cost varies with page count — how much your book costs to produce.
Choosing the wrong trim size creates problems that can't be fixed without reformatting your entire interior. Choose before you design.
KDP's Available Trim Sizes
Amazon KDP supports the following trim sizes for paperback:
Common trim sizes:
| Trim size | Type | Common uses |
|---|---|---|
| 5" × 8" | Pocket book | Compact journals, fiction, poetry |
| 5.06" × 7.81" | Standard novel | Fiction — industry standard for novels |
| 5.5" × 8.5" | Mid-size | Non-fiction, guides, mid-size journals |
| 6" × 9" | Standard non-fiction | Most common: journals, guides, workbooks |
| 7" × 10" | Textbook | Reference books, academic content |
| 8" × 10" | Large non-fiction | Activity books, large-format guides |
| 8.5" × 8.5" | Square | Coloring books, art books |
| 8.5" × 11" | Letter/A4 | Activity books, planners, large print |
Less common but available: 5.25"×8", 5.5"×8.5", 6"×9", 6.14"×9.21", 6.69"×9.61"
Choosing the Right Trim Size
For Low Content Books (Journals, Trackers, Planners)
Recommended: 6"×9"
The most widely used trim size for self-published journals. Advantages:
- Enough page area for tracking layouts and lined pages
- Familiar "standard journal" feel in the hand
- Good balance between page count and printing cost
- Fits in a bag or purse
Use 8.5"×11" when:
- You need large print (seniors, accessibility focus)
- Your layout has complex multi-column tables that need width
- You're publishing full-size planner pages
Use 5"×8" when:
- Targeting a "pocket journal" or "compact daily planner" niche
- Emphasizing portability as a feature
For Coloring Books
Recommended: 8.5"×8.5" or 8.5"×11"
Coloring books need generous page area for detailed illustrations. The square 8.5"×8.5" format is the most common for adult coloring books — it's distinctive and provides good illustration space.
8.5"×11" maximizes illustration area but feels more like a workbook than a coloring book.
For Puzzle Books
Recommended: 8.5"×11" for large print; 6"×9" for standard
Puzzles (word search, sudoku) need clear grid visibility. For large print senior books, 8.5"×11" allows large grid cells without crowding. For standard adult puzzle books, 6"×9" works.
For Non-Fiction Guides and How-To Books
Recommended: 6"×9"
The industry standard for self-help, business, and general non-fiction. Familiar feel, good line length for comfortable reading, efficient per-page content.
Use 7"×10" or 8"×10" if your book has extensive tables, charts, or diagrams that need more horizontal space.
For Fiction
Recommended: 5.06"×7.81" or 6"×9"
5.06"×7.81" is the industry standard for trade paperback fiction. It produces the "mass market feel" buyers recognize. 6"×9" works but produces a book that feels slightly oversized for fiction.
For Children's Books
Recommended: 8"×10" or 8.5"×8.5"
Children's books need larger illustrations and larger text. These trim sizes allow full-bleed illustrations and comfortable reading for young readers.
Trim Size and Printing Cost
Printing cost is based on page count, not physical dimensions. A 150-page 6"×9" book and a 150-page 8.5"×11" book have the same printing cost formula:
$$\text{Cost} = $0.85 + ($0.012 \times \text{pages}) \text{ for B&W}$$
However, a larger trim size fits less text per page — so the same content requires more pages in a larger format.
Example: A 30,000-word guide
- At 6"×9" (250 words/page average): ~120 pages
- At 5"×8" (220 words/page average): ~136 pages
Smaller trim = more pages = slightly higher printing cost for the same content. The difference is minor for most books.
Trim Size and Spine Width
Spine width is calculated from page count and paper type — not trim size. A 120-page book has the same spine width whether it's 5"×8" or 8.5"×11".
Spine text rule: Spine text is only allowed on books with enough spine width to accommodate it — approximately 100+ pages for standard white paper.
Interior Formatting and Trim Size
Your interior must be designed at your chosen trim size. The process:
- Choose trim size before creating your interior
- Set your design canvas to the exact trim size (in Canva, InDesign, or Word)
- Export as PDF at that exact size
- KDP verifies that the uploaded PDF matches the trim size selected in your listing settings
If your PDF doesn't match the selected trim size, KDP's previewer will show formatting errors.
Margins by Trim Size
KDP's minimum margins vary by trim size and page count:
| Trim size | Outside margin | Inside (gutter) margin |
|---|---|---|
| 5"×8" | 0.25" min | 0.375" for under 150 pages |
| 6"×9" | 0.25" min | 0.375" for under 150 pages, 0.5" for 150+ |
| 8.5"×11" | 0.25" min | 0.5"+ for most books |
Gutter margin (inside margin, near the spine) must be larger than the outside margin to ensure text isn't lost in the binding.
Bleed
Bleed applies when any design element extends to the page edge (images, colored backgrounds, lines that touch the border):
- Add 0.125" bleed on all sides
- Your total file dimensions become: trim width + 0.25" × trim height + 0.25"
For a 6"×9" book with bleed: design at 6.25"×9.25"
No bleed is needed if all content stays within the margins (pure text interior).
Changing Trim Size After Publishing
You can change trim size for an unpublished draft. For published books: create a new edition (new listing) with the new trim size. The original stays live until you unpublish it.
Reformatting an interior for a different trim size requires redesigning the layout — page breaks, image sizes, and flow all change. It's significant work. Choose correctly the first time.
Frequently Asked Questions
Can I publish the same book in two trim sizes?
Yes, as separate listings. A standard 6"×9" version and a large print 8.5"×11" version are different products with different ASINs. This is a legitimate series variant strategy.
What is the most popular trim size for KDP journals?
6"×9" is the most common. It's the default mental model for "journal" for most buyers.
Does Amazon offer A4 or other metric sizes?
KDP supports some metric trim sizes, but the available options are primarily in inches. For UK/European market books, the closest available size to A5 (148×210mm) is 5.5"×8.5" or 5.83"×8.27".
Will buyers notice the trim size?
Buyers notice the physical size when they hold the book. A 5"×8" book feels compact; 8.5"×11" feels workbook-sized. Choose a size that matches the physical experience your buyer expects for your niche.
Summary
Trim size decision matrix:
| Book type | Recommended trim |
|---|---|
| Standard journal / planner | 6"×9" |
| Large print journal | 8.5"×11" |
| Pocket journal | 5"×8" |
| Fiction novel | 5.06"×7.81" |
| Non-fiction guide | 6"×9" |
| Activity book / workbook | 8"×10" or 8.5"×11" |
| Coloring book | 8.5"×8.5" |
| Puzzle book (standard) | 6"×9" |
| Puzzle book (large print) | 8.5"×11" |
| Children's book | 8"×10" |
Choose before designing your interior. Design at that exact size. Export at 300 DPI. Upload matching your KDP listing selection.