KDP offers 15 trim sizes ranging from 5” x 8” to 8.5” x 11”, but six account for the vast majority of books published. For genre fiction (romance, thriller, mystery), use 5” x 8” or 5.25” x 8”. For literary fiction, sci-fi, fantasy, and memoir, use 5.5” x 8.5” — the most popular trim size in indie publishing. For non-fiction, use 6” x 9”. An 80,000-word novel produces roughly 340 pages at 5” x 8” (about $4.93 to print on KDP) versus 280 pages at 5.5” x 8.5” (about $4.21) versus 230 pages at 6” x 9” (about $3.61).
This guide covers every available KDP trim size, when to use each one, how size affects your costs, and the one mistake that brands a book as self-published before the reader opens the cover.
Every KDP trim size, smallest to largest
KDP currently supports these trim sizes for paperbacks (all measurements in inches, width x height):
- 5” x 8”
- 5.06” x 7.81”
- 5.25” x 8”
- 5.5” x 8.5”
- 6” x 9”
- 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”
That’s a lot of options. In practice, about six of these account for the vast majority of books published on KDP. The rest are niche formats for art books, children’s books, or specialty publications. Let’s focus on the sizes that matter.
The six trim sizes that matter
5” x 8” — The mass-market standard
Dimensions: 5 inches wide, 8 inches tall
Best for: Romance, thriller, mystery, horror, urban fantasy, cozy mystery — any genre where readers expect a compact, familiar paperback.
Typical page count: 250-400 pages for a 60K-90K word novel.
Why it works: This is close to the traditional mass-market paperback size (4.25” x 6.87”), which has been the standard for genre fiction since the 1930s. Romance alone accounts for over $1.4 billion in annual US sales, and those readers expect a compact, familiar paperback. When a romance reader picks up a 5x8 book, it feels like every other paperback on their shelf. That familiarity is worth more than you think.
The trade-off: The narrow page width means your margins eat a larger percentage of the available space. At 5 inches wide, after subtracting inside and outside margins, you’re left with about 3.5-3.75 inches of text width. That’s comfortable for fiction but tight if you have long words, indented quotes, or any kind of tabular content.
Printing cost: Lower per-page cost because of the smaller paper size, but higher page counts mean you may end up paying similar total costs to a larger trim with fewer pages. Plug your word count into our KDP Book Calculator to compare the actual costs side by side.
5.25” x 8” — The comfortable compact
Dimensions: 5.25 inches wide, 8 inches tall
Best for: Romance, women’s fiction, mystery, thriller — any genre where 5x8 is standard but you want slightly more breathing room.
Typical page count: 230-370 pages for a 60K-90K word novel.
Why it works: That extra quarter inch of width doesn’t sound like much, but it noticeably opens up the text block. You get more comfortable margins without increasing the page count significantly. Many traditionally published trade paperbacks in genre fiction use this size or something close to it.
The trade-off: Negligible. This is a pure upgrade from 5x8 for most genre fiction. The book still feels compact and genre-appropriate in the reader’s hand. The only reason to choose 5x8 over 5.25x8 is if you specifically want the smallest possible footprint.
5.5” x 8.5” — The indie workhorse
Dimensions: 5.5 inches wide, 8.5 inches tall
Best for: Nearly everything. Literary fiction, genre fiction (especially fantasy, sci-fi, and longer novels), memoir, narrative non-fiction, self-help, how-to guides.
Typical page count: 200-350 pages for a 60K-90K word novel, 300-500 for longer works.
Why it works: This is the most popular trim size in indie publishing for a reason. It’s large enough to keep page counts reasonable for longer books (which keeps printing costs down — a 300-page book at this size costs roughly $4.45 to print on KDP), but not so large that it feels like a textbook. The proportions are pleasing. The margins are comfortable. It works on every shelf and is available on both KDP and IngramSpark.
If you’re unsure about your trim size and your book doesn’t fall into a strong genre convention (like romance), pick 5.5x8.5. You almost can’t go wrong. Cambric lets you switch trim sizes and see the page count, margins, and layout update in real time — so you can compare how your book looks at each size before committing.
The trade-off: For shorter genre fiction (romance under 70K words, cozy mysteries), this size can feel too large and airy. The book will have fewer pages, a thinner spine, and may look insubstantial next to traditionally published genre paperbacks.
6” x 9” — The non-fiction standard
Dimensions: 6 inches wide, 9 inches tall
Best for: Non-fiction (business, self-help, academic, reference, history), literary fiction, poetry collections, books with figures or tables, and any book over 100,000 words where you need to control page count.
Typical page count: 180-300 pages for a 60K-90K word book, 250-450 for longer works.
Why it works: The wider page gives you room for more complex layouts — sidebars, pull quotes, wider margins for reader annotations, figures with captions. For non-fiction, this is the format readers expect. The extra real estate also means fewer pages for the same word count, which directly reduces your printing cost.
The trade-off: For genre fiction, 6x9 is almost always wrong. It looks and feels like a non-fiction book. Romance, thriller, and mystery readers will notice — not consciously, but in the “something feels off about this book” way that shapes perception before the first chapter.
7” x 10” — The reference and textbook format
Dimensions: 7 inches wide, 10 inches tall
Best for: Textbooks, workbooks, cookbooks, technical manuals, heavily illustrated non-fiction, coffee table books (budget version).
Typical page count: 150-250 pages for a 60K-90K word book.
Why it works: If your book has wide tables, code samples, full-page diagrams, or needs room for the reader to write, this is the format. The large page allows multi-column layouts, generous margins for notes, and images that don’t have to be crammed into a tiny space.
The trade-off: Expensive to print. Expensive to ship. Not suitable for any kind of narrative fiction. Readers won’t curl up with a 7x10 book — they’ll set it on a desk or a coffee table.
8.5” x 11” — The full-page format
Dimensions: 8.5 inches wide, 11 inches tall (standard US letter size)
Best for: Workbooks, coloring books, activity books, music books, large-format art books, manuals, planners.
Typical page count: Varies widely by content type.
Why it works: When your content needs a full letter-size page — sheet music, full-page illustrations, worksheets with fill-in areas, or large diagrams — this is the only option that makes sense.
The trade-off: The most expensive trim size to print. It doesn’t fit on a standard bookshelf. It doesn’t look like a “book” in the traditional sense. Use this only when the content demands it.
Comparison table: popular KDP trim sizes
| Trim Size | Width x Height | Best Genre | ~Pages (75K words) | Relative Print Cost | Spine Feel |
|---|---|---|---|---|---|
| 5” x 8” | 5” x 8” | Romance, thriller, mystery | 330-360 | Low per page, more pages | Standard paperback |
| 5.25” x 8” | 5.25” x 8” | Genre fiction (all) | 300-340 | Low-medium | Standard paperback |
| 5.5” x 8.5” | 5.5” x 8.5” | Fiction and narrative NF | 270-310 | Medium | Solid paperback |
| 6” x 9” | 6” x 9” | Non-fiction, literary fiction | 220-260 | Medium | Professional |
| 7” x 10” | 7” x 10” | Textbooks, technical | 170-200 | High | Textbook |
| 8.5” x 11” | 8.5” x 11” | Workbooks, planners | 130-160 | Highest | Flat/manual |
Page counts are approximate and depend heavily on font, font size, line spacing, and margin choices. For exact numbers with your word count and formatting settings, use our KDP Book Calculator.
How trim size affects everything else
Page count
This is the most obvious effect. The same 80,000-word novel formatted identically will produce roughly:
- 380 pages in 5” x 8”
- 340 pages in 5.25” x 8”
- 300 pages in 5.5” x 8.5”
- 250 pages in 6” x 9”
Fewer pages means a thinner book, a narrower spine, and lower printing costs. But fewer pages can also make a book feel insubstantial. A 180-page 6x9 novel looks like a novella on the shelf, even if it’s 70,000 words.
Printing cost
KDP charges a fixed fee per book plus a per-page fee. The per-page fee varies by marketplace and ink type (black vs. color), but the relationship is straightforward: more pages = higher printing cost.
However, larger trim sizes use more paper per page, which increases the base cost. So the math isn’t simply “bigger trim = cheaper because fewer pages.” In many cases, 5.5x8.5 hits the sweet spot — enough reduction in page count to offset the slightly higher per-page cost, resulting in the lowest total printing cost for fiction-length manuscripts.
The only way to know for sure is to calculate both. Our KDP Book Calculator does this automatically for every trim size.
Spine width
Your spine width is determined by page count and paper type (white or cream). More pages means a wider spine, which means more room for spine text on your cover. This matters for discoverability on bookstore shelves and in online thumbnails.
A book under about 100 pages has too thin a spine for readable text — KDP requires a minimum of 79 pages for spine text on paperbacks. If your book is short and you’re choosing between trim sizes, a smaller trim (which produces more pages) can give you a usable spine. Our spine width calculator gives you the exact measurement for any page count and paper type.
Reader experience
This is the factor most authors underweight. Your trim size creates an immediate, tactile first impression. Before reading a word, the reader’s hands tell them what kind of book they’re holding.
A compact 5x8 says “genre fiction, beach read, page-turner.” A 6x9 says “serious, substantial, informative.” An 8.5x11 says “reference, workbook, put me on a desk.” These associations are deeply ingrained from years of reading, and fighting them is a losing battle.
Shelf presence
In a bookstore (physical or online), your book sits next to others in its genre. If every other romance novel is 5x8 and yours is 6x9, it sticks out — and not in a good way. It looks like it wandered in from the wrong section.
For online retail, your cover thumbnail is rendered at a fixed height. A taller, narrower book (like 5x8) will appear slightly different than a wider book (like 6x9). This is a minor consideration, but it’s real.
Trim size and margins: the relationship most authors miss
KDP has minimum margin requirements, and these minimums change based on your page count. But here’s what most guides don’t explain clearly: the inside margin minimum is about page count, not trim size. A 300-page book needs a 0.5” inside margin whether it’s 5x8 or 6x9.
What changes with trim size is how much usable space you have left after margins. On a 5-inch-wide page with a 0.75” inside margin and 0.5” outside margin, your text block is 3.75 inches wide. On a 6-inch-wide page with the same margins, it’s 4.75 inches wide. That extra inch is significant — it’s the difference between 10-11 words per line and 13-14 words per line.
The ideal line length for comfortable reading is 60-75 characters (roughly 10-13 words). If your combination of trim size, margins, and font size produces lines longer than about 80 characters, reading becomes fatiguing. If lines are shorter than 45 characters, the constant line-breaking disrupts flow. For reference, a 5.5” x 8.5” page with 0.75” inside and 0.55” outside margins using 11pt Garamond produces lines of approximately 65 characters — right in the sweet spot.
This is where trim size, margins, and font choice all interact. A larger trim size gives you more room, but that room only helps if you use it for wider margins (more white space, more breathing room) rather than cramming more text per line. For a deeper look at how font and size choices interact with your trim and margins, see our Book Font Preview tool.
Practical recommendation: Use the KDP minimums as a floor, then add at least 0.125”-0.25” to each margin. Professional books are generous with white space. Cramped margins are one of the fastest tells of amateur formatting. Our margin calculator shows recommended margins for any trim size and page count combination, following the same conventions used in traditionally published books.
The #1 trim size mistake: 6x9 for genre fiction
This comes up constantly, and it’s worth addressing directly. New indie authors often choose 6x9 for their genre fiction novel — romance, thriller, mystery, fantasy — because it feels like the “default” or because they want fewer pages.
Don’t do this.
Genre fiction readers have been conditioned by decades of mass-market and trade paperbacks in the 5”-5.5” width range. When they pick up a 6x9 novel, it feels like a non-fiction book. It’s too wide, too tall, and the proportions signal “this is an informational book” rather than “this is a story.”
The cost savings from fewer pages are real but marginal. For a 75,000-word novel, the difference in printing cost between 5.5x8.5 and 6x9 might be $0.30-$0.50 per copy. That’s not worth the reader perception mismatch.
When 6x9 is right for fiction: Literary fiction and upmarket fiction can carry a 6x9 format. These books are already positioned as “serious” reads, and the larger format reinforces that positioning. Epic fantasy doorstopper novels (150K+ words) sometimes benefit from 6x9 to keep the page count under 500. But for standard genre fiction, stick with 5x8, 5.25x8, or 5.5x8.5. Cambric lets you switch trim sizes and see the result instantly in a live preview, so you can compare how your book looks at different sizes before committing.
How trim size affects KDP printing costs
KDP’s printing cost formula has two components:
- Fixed cost — A base charge per book (varies by marketplace)
- Per-page cost — A charge per page (varies by ink type and marketplace)
For black-and-white interiors on the US marketplace (as of early 2026), the math works out roughly like this per KDP’s printing cost calculator:
- Fixed cost: ~$0.85 per book
- Per-page cost: ~$0.012 per page
So a 300-page book costs about $0.85 + (300 x $0.012) = $4.45 to print. A 250-page book costs about $0.85 + (250 x $0.012) = $3.85 to print. For color interiors, the per-page cost jumps to roughly $0.065-$0.07, making a 300-page color book approximately $20.35 to print.
The larger the trim size, the fewer pages you get for the same word count — so your per-page charges go down. But KDP doesn’t currently charge a different per-page rate for different trim sizes in black-and-white (color is different). This means a larger trim genuinely costs less to print for the same manuscript, page-for-page.
However, the savings flatten out quickly. Going from 5x8 to 5.5x8.5 might save you $0.50-$0.80 per copy. Going from 5.5x8.5 to 6x9 saves another $0.30-$0.50. At some point, the reader-experience cost outweighs the printing savings.
A note on IngramSpark trim sizes
If you distribute through IngramSpark in addition to KDP, you’ll find that most trim sizes overlap. IngramSpark supports all the popular sizes (5x8, 5.25x8, 5.5x8.5, 6x9, 7x10, 8.5x11) plus some additional options like 5” x 7” and 5.5” x 7.5” that KDP doesn’t offer.
The key differences:
- IngramSpark has a few trim sizes KDP doesn’t, and vice versa. If you plan to distribute through both, check that your chosen trim size is available on both platforms before you commit.
- IngramSpark’s PDF requirements are slightly stricter (PDF/X-1a:2001 preferred, CMYK for color).
- Margin minimums are essentially the same, but IngramSpark documentation sometimes states them differently.
If you format your book for the stricter of the two platforms’ requirements, it will pass on both. Cambric targets the stricter specification by default, so PDFs exported from it are accepted by both KDP and IngramSpark without modification. For a detailed side-by-side comparison, see our KDP vs IngramSpark breakdown. For more on the full formatting workflow, see our complete KDP formatting guide.
Quick decision framework
Still not sure? Here’s the short version:
- Writing romance, mystery, thriller, horror, or cozy? Go with 5” x 8” or 5.25” x 8”.
- Writing sci-fi, fantasy, literary fiction, or memoir? Go with 5.5” x 8.5”.
- Writing non-fiction (business, self-help, history)? Go with 6” x 9”.
- Writing a textbook, workbook, or heavily illustrated book? Go with 7” x 10” or 8.5” x 11”.
- Not sure and just want something safe? 5.5” x 8.5” works for nearly everything.
The easy way
Every decision in this guide — trim size, margins that match your page count, font size that produces comfortable line lengths, the interaction between all of these variables — is something you can calculate manually. But it’s also something your formatting tool should handle for you.
Cambric lets you set your trim size and instantly see how your book looks at that size, with margins, fonts, and page count adjusted automatically. Switch between 5x8 and 5.5x8.5 and see the difference in real time, on a realistic book preview, before you commit. No uploading PDFs to KDP to check if they pass. No guessing about margins. It’s a $109 one-time purchase desktop app with 20+ professional templates that all support every trim size listed in this guide.
Pick the size that matches your genre. Use the margin calculator to confirm your margins are correct. Let the tool handle the math. Spend your time writing the next book.