Trim size is the most consequential decision an author makes about how their book looks, and most authors make it without quite realising they're making it. Pick the right trim and the book reads correctly on the shelf; pick a slightly wrong one and the same prose feels textbook-ish, or pamphlet-ish, or budget-ish — none of which the writing deserves.
This note walks through the trim sizes Amazon KDP supports for paperback (most of which apply to hardback too), what each one signals to a reader, and when a custom trim is worth the trouble.
What trim size is, mechanically
Trim is the finished page size after printing and cutting. A trim of 6 × 9 means each page is 6 inches wide and 9 inches tall when the book is in your hands. KDP maintains a list of supported trims and a published page-count range for each; outside that range a given trim cannot be printed.
Trim affects everything downstream: text block width, font size, line length, gutter, spine, cover dimensions, and how the book physically sits on a shelf or in a hand. It is set at the start of layout and effectively cannot be changed without reflowing the entire interior.
The shape of the choice
KDP supports roughly twenty trim sizes for paperback. Most indie titles use one of six, and those six divide cleanly by what they're for.
Novel-shaped — taller than wide, narrow
- 5 × 8 in. Compact. Reads as a popular novel; sits well in one hand. The closest KDP gets to a mass-market paperback feel.
- 5.25 × 8 in. A trade-paperback novel size, a touch wider than 5 × 8. Quiet, traditional.
- 5.5 × 8.5 in. The most common indie default. Wider than a novel strictly needs, but the cover surface is larger and the page count goes further.
Non-fiction-shaped — taller than wide, wider
- 6 × 9 in. The most popular non-fiction trim. Generous page width, room for a wider text block, supports inset images and tables without crowding. Reads as a serious, considered title.
- 6.14 × 9.21 in. UK royal octavo. Less common in indie publishing, more common in traditional UK trade non-fiction.
- 7 × 10 in. Workbooks, textbooks, instructional non-fiction. Large pages that hold tables, diagrams or exercise space comfortably.
Picture-book and landscape
- 8 × 10 in (portrait). Children's picture books and illustrated titles.
- 8.5 × 8.5 in (square). Square children's books and photo books. The square trim is conspicuous on a shelf; it signals "picture book" to a buyer at a glance.
- 8.25 × 6 in (landscape). Landscape children's books, panoramic photo books.
Low-content
- 8.5 × 11 in. Journals, planners, workbooks, notebooks. The largest standard size. Reads as a working document rather than a book to read.
- 6 × 9 in. Common for guided journals that want to feel more book-like and less workbook-like.
What each trim signals
Trim size is a genre signal whether you intend it or not. A reader scanning a shelf reads three things in the first half-second: cover artwork, title typography, and shape of the book. Get the shape wrong and the cover has to work twice as hard.
A few quick conventions, with the caveat that nothing about trim is a hard rule — only a strong default.
- A novel at 6 × 9 reads as a debut by someone who didn't know. That width belongs to non-fiction; on a novel it gives a textbookish feel. Strong novels at 6 × 9 exist; their authors usually had a reason.
- Non-fiction at 5 × 8 reads as a personal essay or memoir. Fine for a memoir; less ideal for a manual, a guide or a serious reference.
- A workbook at 6 × 9 will feel cramped — there isn't enough page width for exercise space or worked examples.
- A children's book at 5 × 8 will read as a chapter book rather than a picture book — the page is too narrow for illustration spreads.
- Cookbooks at 5.5 × 8.5 are possible but read as recipe pamphlets rather than cookbooks; a wider trim flatters food photography.
When the manuscript is borderline — a long-form essay collection, a memoir-with-research, a novella with prefatory material — pick the trim that matches the dominant register of the text. Long essays at 6 × 9, memoir at 5.25 × 8 or 5.5 × 8.5.
What changes between trims
The same manuscript at 5 × 8 and at 6 × 9 will not have the same page count. Trim is a multiplier on every layout decision downstream.
- Page count drops as the page gets bigger. A 70,000-word novel at 5 × 8 with a 10 pt body type might run 280 pages; at 6 × 9 the same text drops to around 240. Spine width follows.
- Cover dimensions change. A new trim means a new cover from scratch. The artwork survives; the layout does not.
- Royalty changes. KDP's print cost increases with page count and trim area. A larger trim costs more to print per copy, but a smaller page count partially offsets that.
- Shelf appeal changes. Smaller trims are easier to fit on a bookshop shelf, but at indie volume that's rarely the constraint. Online listings show all trims at the same thumbnail size.
The honest summary: choose the trim that matches the genre, then accept the production consequences. Don't optimise for royalty per copy by squeezing a non-fiction title into a 5 × 8 trim — the saving is small and the reader sees a smaller, cheaper-looking book.
When custom trim makes sense
KDP allows custom trim sizes within a range — 4 × 6 in minimum up to roughly 8.5 × 11 in, depending on binding and paper. The temptation is to pick something distinctive.
Resist it, almost always. The reasons:
- Templates and tools don't know your trim. Most cover design tools default to KDP's standard list. A custom trim means setting up the canvas manually every time and double-checking the export.
- Custom doesn't print cheaper than the nearest standard. KDP rounds custom trims up to the next print-cost band; you save nothing.
- The shelf reads it as wrong. A 5.5 × 7.75 in book looks like a 5.5 × 8.5 in book that was cut a quarter-inch short. Custom trims that hover near a standard size read as production errors.
- Some KDP features expect a standard trim. Hardback availability is patchier on custom trims; some Expanded Distribution programmes only accept standard sizes.
There are real cases for custom trim — landscape photo books with a specific aspect ratio, square art books at an unusual size, gift editions where the trim is part of the design. They are rare. If you can't articulate exactly why a standard trim won't serve the book, use a standard trim.
A small decision framework
If trim is undecided:
- Novel, novella, story collection → 5 × 8 or 5.25 × 8 for compact, 5.5 × 8.5 for trade-default.
- Memoir, personal essay → 5.25 × 8 or 5.5 × 8.5.
- General non-fiction, business, self-help → 6 × 9.
- Reference, textbook, technical manual → 6 × 9 or 7 × 10.
- Workbook, planner, journal, logbook → 7 × 10 or 8.5 × 11.
- Cookbook with photography → 7 × 10 or 8.5 × 8.5.
- Children's picture book → 8 × 10 portrait or 8.5 × 8.5 square.
- Photo book, art book → 8.5 × 8.5 or a considered larger size.
That covers the vast majority of indie titles, and the cases where it doesn't are usually books that already know what they need to be.
Where Folio Format fits
Folio Format presents the supported KDP trims as a clear list at the start of a book project, with a hint of what each one is typically used for, and a preview of how the chosen trim affects the text block, margins and pagination before the first paragraph is set. The choice is reversible up until the first export, and the implications — page count estimate, cover dimensions, royalty implications — recompute as the trim changes.
Last checked 22 May 2026. Always confirm current Amazon KDP and IngramSpark specifications before uploading final files. Folio Format is designed to help users export KDP-ready files and catch common publishing issues before upload; it makes no claim about platform acceptance.