How to Choose a Trim Size for Your Novel
Trim size is the width and height of the finished, cut page. For most fiction the usual choices are 5×8, 5.25×8, 5.5×8.5 and, in the UK, B-format (about 5.06×7.81). 6×9 is the self-publishing default and common for literary fiction, but it can read as big for a genre paperback. Pick the trim before anything else, because it changes your page count, your margins and your print cost.
Trim size is the size of the finished page, after the printer has cut it. It’s the first formatting decision you make, and most of the others follow from it, so it’s worth a few minutes before you do anything else.
The usual fiction trims
| Trim | Where you see it |
|---|---|
| 4.25×6.87″ | Mass-market paperbacks. Dense and portable. |
| 5×8″ | Genre paperbacks and novellas. |
| 5.06×7.81″ (B-format) | The standard UK and European paperback novel. |
| 5.25×8″ | Very common for US genre fiction. |
| 5.5×8.5″ | Roomy. YA and literary fiction. |
| 6×9″ | The self-publishing default. Literary fiction, memoir, non-fiction. |
If you’re not sure, measure three or four books like yours from your own shelf and match them. Amazon lists every size it supports, with the page limits for each, in its print options.
How trim changes the page count
The part people miss: a smaller trim doesn’t make a smaller book, it makes a thicker one. The same 90,000 words run to more pages at 5×8 than at 6×9, which raises the print cost and widens the spine.
That matters for two reasons. Print-on-demand charges per page, so trim is one of the few levers you have on cost (there’s a worked example in KDP royalties explained). And the spine width on your cover depends on the final page count, which depends on the trim. Change the trim late and the cover file and your KDP margins are both wrong.
Matching what readers expect
Readers have expectations about size they couldn’t explain. A beach-read thriller at 6×9 can feel oversized, because a lot of people associate 6×9 with non-fiction. A dense literary novel at 5×8 can feel cramped. Your readers learned what your genre should feel like from the books on their shelves, so you might as well match them.
How Galley does it
Galley offers six trims: mass market (4.25×6.87″), small trade (5×8″), B-format (5.06×7.81″), digest (5.5×8.5″), US trade (6×9″) and Royal (6.14×9.21″). A Japanese book also gets the six Japanese formats KDP prints. There’s no 5.25×8. You pick a trim when you create the book and you write on that page, so there’s no guessing how the text will reflow later. You can change it from the editor toolbar while you write, and the page changes with it.
To see the sizes side by side first, the trim size comparison draws each one at true scale, and word count to page count tells you what your word count runs to in each.
More on formatting
- What Is a Dinkus? Scene Breaks in a Printed NovelWhat a dinkus is, the other marks novels use for a scene break, and why a blank line on its own goes wrong at the bottom of a printed page.
- Running Heads and Folios: The Top and Bottom of a Book PageWhat goes in the running head of a novel, where the page numbers sit, and the pages that should carry neither.
- Book Margins and the Gutter: The Numbers for KDPKDP's minimum margins by page count, why the inside margin (the gutter) has to grow as a book gets thicker, and what margins a novel should actually use.