How to Choose the Right Trim Size for Your Book
Trim size is the physical dimensions of your finished book (width × height), and you choose it before formatting because everything else depends on it. Pick by genre convention first: most novels use 5×8″ or 5.25×8″, non-fiction and memoir often 5.5×8.5″ or 6×9″, and larger 7×10″ or 8×10″ sizes suit workbooks, textbooks and image-heavy books. Trim size also affects page count and printing cost: a smaller trim means more pages (and can cost more to print); a larger trim means fewer, denser pages. Match your genre's norms so your book looks right on the shelf, then confirm the size is supported by your printer. Here's how to decide.
Trim size is one of the first decisions you make — and one of the most consequential, because your margins, page count, cover dimensions and even printing cost all flow from it. Choose it before you format, not after. Here's how to pick the right one.
What is trim size?
Trim size is the width and height of your printed book after it's been trimmed to its final dimensions, written as width × height in inches (e.g. 6×9″). It's the physical footprint of your book. Because the whole interior is laid out to fit that page, you set it up front — changing it later means re-formatting the entire book.
Standard trim sizes by genre
| Book type | Common trim sizes |
|---|---|
| Fiction / novels | 5×8″, 5.25×8″, 5.5×8.5″ |
| Non-fiction / memoir | 5.5×8.5″, 6×9″ |
| Trade paperback (general) | 6×9″ |
| Workbooks / journals | 7×10″, 8×10″, 8.5×11″ |
| Children's picture books | 8×8″, 8×10″, 10×8″ |
| Photo / art books | Large & often square |
These conventions exist for a reason — readers and bookstores expect a novel to feel like a novel. Matching them makes your book look professionally produced; ignoring them makes it look off, even if readers can't say why.
How trim size affects page count and cost
This is the part beginners miss: your trim size changes how many pages your book has, and page count drives print cost.
- Smaller trim (e.g. 5×8″): less text per page → more pages → a thicker book and potentially higher print cost.
- Larger trim (e.g. 6×9″): more text per page → fewer pages → a slimmer, often cheaper-to-print book.
- Print cost is driven by page count, so trim size indirectly affects your per-copy cost and therefore your pricing and royalty.
For a long novel, a slightly larger trim can meaningfully reduce page count and cost; for a short book, a smaller trim adds welcome thickness so it doesn't feel flimsy.
Other things that should influence your choice
- Content: image-heavy or table-heavy books need larger trims; simple text is fine small.
- Genre expectations: check what bestsellers in your category actually use.
- Reading comfort: very small trims can feel cramped; very large ones are awkward to hold for fiction.
- Printer support: confirm your trim is offered by KDP and/or IngramSpark, and whether it's an “expanded distribution” size (some sizes are required for bookstore distribution).
How to decide, step by step
- Identify your genre and look up the sizes its bestsellers use.
- Consider your content — images, tables and workbooks push you larger.
- Check the effect on page count if length or cost is a concern.
- Confirm the size is supported by your printer and distribution plan.
- Lock it in before formatting — then design the interior to that page.