What Trim Size Should You Choose for Your Self-Published Book?

Your self-published book trim size should be 6” × 9” if you are writing general nonfiction, memoir, or literary fiction — it is the most widely used trade paperback dimension, supported by every major print-on-demand platform, and matches what readers expect to find in bookstores. For genre fiction like romance or thriller, 5” × 8” or 5.5” × 8.5” works better, while specialty books like cookbooks and children’s picture books require their own specific dimensions based on content needs.

What Is Trim Size and Why Does It Matter?

Trim size is the final width-by-height measurement of your printed book after the pages have been cut to their finished dimensions. It is always expressed as width × height — so a 6” × 9” book is six inches wide and nine inches tall.

This is one of the first decisions you need to make before formatting your interior, because everything downstream depends on it: your margin settings, your line length and readability, your page count, your spine width, and ultimately your per-unit printing cost. If you change your trim size after formatting, you will need to reflow your entire manuscript.

Trim size also sends a signal to readers. A book that matches the standard dimensions for its genre looks professional and feels familiar in a reader’s hands. A novel printed at 8.5” × 11” would feel like a school report, while a business book printed at 4.25” × 6.87” (mass-market size) would seem out of place. Matching genre conventions is one of the simplest ways to make your self-published book look traditionally published.

What Trim Size Does Your Genre Expect?

Every genre has established size norms shaped by decades of reader expectations. Pick up a handful of traditionally published books in your genre and you will see consistent patterns.

Fiction (novels): Most literary and genre fiction uses 5” × 8”, 5.25” × 8”, or 5.5” × 8.5”. These digest-sized formats feel comfortable in one hand, fit easily in a bag, and produce a page count that feels substantial without being bloated. The 5.5” × 8.5” size is particularly popular with self-published fiction authors because it is supported across all platforms and keeps printing costs reasonable.

Nonfiction, memoir, and business books: The standard here is 6” × 9”, which is the true trade paperback size. Walk through the nonfiction section of any bookstore and you will see this dimension everywhere. It provides enough page width for comfortable reading and accommodates footnotes, pull quotes, and sidebars without crowding.

Children’s picture books: These require larger formats to give illustrations room to breathe — common sizes include 8.5” × 8.5” (square), 10” × 8” (landscape), and 8.5” × 11” (portrait). The choice depends on your illustration style and layout.

Cookbooks and photography books: A 7.5” × 9.25” or 8” × 10” format works well, providing enough space for full-page images alongside text. Cookbooks need to be large enough for recipes to be readable at arm’s length on a kitchen counter.

Poetry and chapbooks: Smaller, more intimate sizes like 5” × 8” or 5.5” × 8.5” suit poetry collections. The generous white space on a smaller page emphasizes each poem’s visual presentation.

Textbooks and workbooks: The 7” × 10” or 8.5” × 11” sizes are standard, accommodating diagrams, tables, and margin notes that educational content requires.

Which Trim Sizes Do KDP, IngramSpark, and Draft2Digital Support?

Each platform publishes its own list of supported dimensions, and choosing a size that works across all the platforms you plan to use saves reformatting headaches later.

Amazon KDP supports a wide range of trim sizes and lists five as its most popular: 5” × 8”, 5.25” × 8”, 5.5” × 8.5”, 6” × 9”, and 6.14” × 9.21”. KDP also supports custom sizes within its minimum and maximum bounds, giving you flexibility if your book requires a non-standard dimension.

IngramSpark supports paperback books with white paper from 4” × 6” up to 8.5” × 11”. If you choose crème or groundwood paper (common for fiction), the maximum size narrows to 6.14” × 9.252”. This is an important constraint — if you want a crème-paper novel larger than roughly 6” × 9”, IngramSpark will not print it. For details on how page margins interact with your chosen trim size, you will want to check your platform’s specific margin requirements.

Draft2Digital Print supports a set of standard trim sizes and requires all books to be between 64 and 740 pages. If your manuscript falls below 64 pages at your chosen trim size, you may need to size up to increase the page count.

Reedsy Studio exports manuscripts in four preset sizes: Pocket (4.25” × 6.87”), Reedsy (5” × 8”), Digest (5.5” × 8.5”), and Trade (6” × 9”). If you use Reedsy for formatting, you are limited to these four options.

The safest approach is to choose a trim size that appears on every platform’s supported list. The 5.5” × 8.5” and 6” × 9” sizes are universally supported and give you the most distribution flexibility.

How Does Trim Size Affect Your Printing Costs?

Trim size directly influences your per-unit printing cost through its effect on page count. A smaller trim size means fewer words fit on each page, which increases your total page count. More pages mean more paper and more ink, which raises the printing cost per copy.

For example, a 70,000-word novel formatted at 5” × 8” might run 320 pages, while the same manuscript at 6” × 9” might be only 240 pages. On a print-on-demand platform where you pay per page, that 80-page difference translates directly into a higher unit cost — which either cuts into your margin or forces you to raise your retail price.

Standard trim sizes are also more cost-efficient than custom ones. Print-on-demand printers optimize their equipment and paper sheets around standard dimensions. A non-standard size can result in more paper waste during trimming, and some printers charge a premium for custom sizes. Sticking with a standard dimension like 5.5” × 8.5” or 6” × 9” keeps your costs predictable and competitive.

Your trim size also affects your spine width calculation, which in turn affects your cover design. A higher page count from a smaller trim size means a wider spine — something your cover designer needs to account for.

What Technical Adjustments Does Your Trim Size Require?

Once you have chosen a trim size, your manuscript file must be set up to match it exactly. The page dimensions in your Word document or InDesign file should equal your chosen trim size.

Margins: KDP requires minimum interior margins of 0.25” on all sides for books without bleed, and 0.375” for books with bleed. The inside (gutter) margin needs to be wider to account for the binding — typically 0.5” to 0.875” depending on your page count. A 300-page book needs a wider gutter than a 100-page book because the pages curve more steeply into the spine.

Bleed: If any images or design elements extend to the edge of the page, you need 0.125” (3.2mm) of bleed on the top, bottom, and outside edges. This extra margin gets trimmed off during manufacturing, ensuring clean edges with no white strips. Most text-only novels do not need bleed, but books with full-page images, colored backgrounds, or decorative elements do.

Interior images: All raster images in your interior should be at least 300 DPI at print size. A lower DPI will result in fuzzy or pixelated output when printed. Your trim size determines how large each image needs to be in pixels — a full-width image in a 6” × 9” book needs to be at least 1800 pixels wide (6 inches × 300 DPI).

PDF export: Your final interior PDF must match your trim size exactly. If your trim size is 6” × 9” with bleed, your PDF page dimensions should be 6.25” × 9.25” (the trim size plus bleed on three sides). Mismatched dimensions are one of the most common reasons platforms reject uploaded files.

Should You Use a Different Trim Size for Hardcover?

Hardcover editions typically use slightly larger trim sizes than their paperback counterparts. A novel published as a 5.5” × 8.5” paperback might be released as a 6” × 9” hardcover. This size difference is partly tradition — hardcovers have historically been larger — and partly practical, since the case binding adds bulk and a slightly larger interior page helps balance the proportions.

Not all trim sizes available for paperback are available for hardcover on every platform. KDP and IngramSpark both support hardcover printing, but their lists of supported hardcover dimensions are smaller than for paperback. Check the specific platform’s hardcover specifications before committing to a size.

If you plan to release both a paperback and hardcover edition, consider your pricing strategy. Hardcovers command higher retail prices, and a slightly larger trim size reinforces the premium feel. However, using two different trim sizes means maintaining two separate interior files with different margin settings — something to factor into your production workflow.

Frequently Asked Questions

What is the most popular trim size for self-published books?

The 6” × 9” trim size is the most popular for self-published nonfiction and the most widely used trade paperback dimension overall. For fiction, 5.5” × 8.5” and 5” × 8” are equally common. These three sizes are supported by every major print-on-demand platform including KDP, IngramSpark, and Draft2Digital.

Can I change my trim size after publishing?

You can update your trim size on most platforms by uploading a new interior file, but it requires reformatting your entire manuscript — margins, page breaks, headers, footers, and image placement all change. Your cover file will also need to be regenerated with the new spine width. It is much easier to choose the right trim size before you begin formatting.

Does trim size affect my ebook?

No. Trim size is a print-only specification. Reflowable ebooks (EPUB and MOBI) adapt to whatever screen the reader uses, so trim size is irrelevant. Fixed-layout ebooks do have set page dimensions, but these are specified independently from any print trim size.

What trim size should I use if I want my book in bookstores?

Bookstores expect standard trade sizes — 5.5” × 8.5” or 6” × 9” for most genres. Non-standard sizes can create shelving problems and make your book look out of place. If bookstore distribution through IngramSpark is part of your plan, stick to a size that matches traditionally published books in your category.

Is 5” × 8” too small for a nonfiction book?

For most nonfiction, yes — 5” × 8” produces narrow text columns that can feel cramped, especially if your content includes tables, charts, or footnotes. The 6” × 9” format gives nonfiction authors significantly more usable page width. However, 5” × 8” works well for short nonfiction like devotionals, gift books, or essay collections where a compact feel is intentional.