Ash Davies
Founder of Books.by · Helped 20,000+ authors self-publish since 2014
The complete guide to standard book sizes, trim dimensions by genre, printing costs, and how to choose the right size for your self-published book.
📖 Quick reference: For a shorter overview, see our trim sizes glossary entry.
Trim size — the final width and height of your printed book — is one of the most important decisions you'll make as a self-published author. It's not just a technical spec. Your book's trim size directly affects:
Most guides overcomplicate this. There's no single "right" book size. The perfect trim size depends on your genre, your content type, your audience's expectations, and your budget. A romance novel, a business book, and a children's picture book all have different ideal sizes. Readers instinctively know when something feels "off."
We'll walk you through every standard book size, recommend the best trim size for each genre, show you how size affects your printing costs and royalties, and give you a simple framework for making the right choice. By the end, you'll know exactly what size to pick.
From our team: "Based on 12,000+ books published through Books.by, 5×8 and 5.5×8.5 account for over 70% of all orders. When in doubt, start there." — Ash Davies, Founder
These rectangles show the relative proportions of the most common trim sizes.
The publishing industry has settled on a handful of standard trim sizes over the past century. Print-on-demand services like Books.by, Amazon KDP, and IngramSpark all support these sizes. They're what readers expect to find on shelves and in their hands.
Here's a complete reference of every standard book size, with dimensions in both inches and millimetres:
| Size Name | Dimensions (in) | Dimensions (mm) | Best For | Pros | Cons |
|---|---|---|---|---|---|
| Mass Market Paperback | 4.25" × 6.87" | 108 × 175 | Genre fiction (romance, thriller, sci-fi) | Cheap to print, fits in pockets & purses | Small text, not great for non-fiction |
| Trade Paperback (Small) Most Popular | 5" × 8" | 127 × 203 | Literary fiction, general non-fiction | Best balance of cost & readability | Can feel small for image-heavy books |
| Trade Paperback (Standard) Popular | 5.5" × 8.5" | 140 × 216 | Non-fiction, memoirs, business books | Feels substantial, comfortable to read | Slightly higher print cost than 5×8 |
| Trade Paperback (Large) | 6" × 9" | 152 × 229 | Textbooks, reference, non-fiction, poetry | Great for images, charts, tables | Higher print & shipping costs |
| Royal | 6.14" × 9.21" | 156 × 234 | UK trade standard | Standard outside US | Less common in US market |
| Executive | 7" × 10" | 178 × 254 | Textbooks, workbooks | Spacious layout, room for margins | Higher cost, heavy |
| US Letter | 8.5" × 11" | 216 × 279 | Workbooks, activity books, cookbooks | Maximum space for content | Expensive to print & ship |
| A5 (International) | 5.83" × 8.27" | 148 × 210 | Fiction & non-fiction outside US | Global standard, familiar worldwide | Less common in US bookshops |
| A4 (International) | 8.27" × 11.69" | 210 × 297 | Workbooks, textbooks, portfolios | International standard for large format | Very large, expensive |
| Small Square | 7.5" × 7.5" | 190 × 190 | Children's books, photo books | Eye-catching, unique on shelf | Limited text per page |
| Square | 8.5" × 8.5" | 216 × 216 | Coffee table books, cookbooks, art | Perfect for image-forward books | Higher cost, specialized use |
The US market predominantly uses inch-based sizes (5" × 8", 6" × 9"), while the UK, Europe, Australia, and much of the rest of the world prefers A-sizes (A5, A4) or Royal (6.14" × 9.21"). If you're selling primarily outside the US, consider A5 or Royal. If selling globally through Books.by, the US trade sizes work everywhere — they're recognised internationally even if they're not the local standard.
Every genre has a "standard" size that readers expect. Here's what to use for yours.
Your trim size directly impacts your per-copy printing cost — and therefore your royalties. Here's the simple rule: bigger books cost more to print. They use more paper, weigh more (higher shipping costs), and take longer to produce.
But there's a nuance most authors miss: the same manuscript produces fewer pages in a larger trim size. So while a 6" × 9" book costs more per page than a 5" × 8", it might have fewer pages, partially offsetting the higher per-page cost.
Books.by uses a simple, transparent pricing model. No hidden fees. No surprises on your royalty statement:
These costs are the same regardless of trim size. Larger sizes mean fewer pages for the same word count, which reduces your total printing cost. Authors keep an average of $4.73 more per paperback through Books.by vs Amazon.
Here's what a 200-page book costs to print at different sizes with black & white interior:
| Trim Size | Est. Pages (60K words) | B&W Print Cost | Colour Print Cost | Savings vs 5×8 |
|---|---|---|---|---|
| 5" × 8" | 280 pages | $5.74 | $11.46 | — |
| 5.5" × 8.5" | 240 pages | $5.10 | $10.02 | Save $0.64 |
| 6" × 9" | 210 pages | $4.62 | $8.94 | Save $1.12 |
The right size isn't just about cost. Reader expectations and genre conventions matter more. But understanding the cost implications helps you make an informed decision and set the right retail price for your target royalty.
From our team: "We think 5.5×8.5 is the single best all-around trim size. It works for fiction, non-fiction, and memoir. It keeps costs down while looking professional on any shelf. If you're agonising over this decision, just pick 5.5×8.5 and move on to writing your next book." — Ash Davies, Founder
Use the Books.by royalty calculator to see exactly how different trim sizes affect your per-sale earnings at various price points.
Still not sure? Walk through these six steps and you'll land on the right size every time.
This is the biggest factor. Romance → 5" × 8". Business book → 5.5" × 8.5" or 6" × 9". Children's picture book → 8.5" × 8.5". Start with the genre recommendations in Chapter 3 above.
Does your book have images, charts, tables, diagrams, or illustrations? If yes, go larger. Visual content needs space to breathe — cramped images look unprofessional. For image-heavy books, 6" × 9" is the minimum; consider 8.5" × 11" for workbooks and art books.
A very short book (under 100 pages) benefits from a smaller trim size so it doesn't feel flimsy. A very long book (400+ pages) benefits from a larger trim size to keep the spine manageable. Use the page count estimates in Chapter 6.
Selling in physical bookshops? Match the standard shelf size for your genre — bookshops group books by genre, and yours should fit in. Selling online only through Books.by? You have more flexibility, but genre norms still matter for reader expectations.
Find 5 bestselling books in your genre — on Amazon, at a bookshop, or on your shelf. Check their trim sizes (Amazon lists them in "Product details"). If they're all 5.5" × 8.5", that's your answer.
Still torn between two sizes? Order proof copies in both. Hold them. Read a chapter. Show them to friends. The right size will feel obvious in your hands. Books.by proof copies are printed at cost — it's worth the small investment to get it right.
The same manuscript will produce very different page counts depending on your trim size. Here's what a typical 60,000-word manuscript (about average for a novel or non-fiction book) looks like:
That's a 70-page difference between the smallest and largest common trade sizes. This matters for both printing costs (as we covered) and reader perception — a 280-page 5×8 book feels like a more substantial read than a 210-page 6×9, even though the content is identical.
Print-on-demand services have minimum and maximum page count requirements:
If your manuscript is very long, you may need a larger trim size just to stay within page limits. Alternatively, consider splitting into two volumes.
Proper margins are essential for readability and professional appearance. Here are the recommended minimums:
If your book has images, colours, or design elements that extend to the edge of the page, you need bleed. Bleed means your document is slightly larger than the final trim size — typically 0.125" (3mm) added to each edge.
Enter your word count below to see exactly how many pages your book will be at different trim sizes — plus the estimated printing cost and spine width.
Books.by supports 13+ trim sizes covering everything from pocket-sized novellas to large-format art books. Here's the complete list:
| Size Name | Dimensions | Popularity |
|---|---|---|
| Pocket (Mass Market) | 4.25" × 6.87" | Genre fiction |
| Trade Paperback (Small) | 5" × 8" | #1 on Books.by |
| Digest | 5.5" × 8.5" | #2 on Books.by |
| A5 (International) | 5.83" × 8.27" | Popular outside US |
| US Trade | 6" × 9" | Top 3 |
| Royal | 6.14" × 9.21" | UK standard |
| Comic | 6.63" × 10.25" | Comics & graphic novels |
| Executive | 7" × 10" | Textbooks |
| Small Square | 7.5" × 7.5" | Children's books |
| Square | 8.5" × 8.5" | Coffee table books |
| A4 (International) | 8.27" × 11.69" | International workbooks |
| US Letter | 8.5" × 11" | Workbooks & planners |
| Small Landscape | 9" × 7" | Children's picture books |
| Landscape | 11" × 8.5" | Photography & art |
Books.by prints from facilities in the USA, UK, Europe, and Australia. Your readers get fast, local shipping regardless of location. Books.by authors in 43 countries use these sizes daily. All 13+ sizes are available at all print locations. See our full printing & sizes page for more details on paper types, binding options, and fulfilment regions.
One of the best ways to validate your trim size choice is to look at what the Big Five publishers use for bestselling books in your genre. Here's a snapshot of some recent bestsellers:
Notice the pattern? Fiction clusters around 5" – 5.5" wide and 8" – 8.5" tall. Non-fiction and memoir trend slightly larger. Business/self-help books are consistently around 5.5" × 8.25".
Major publishers don't always use exact "standard" sizes — they sometimes use custom dimensions like 5.31" × 8" or 5.8" × 8.5". As a self-publisher using print-on-demand, you'll choose from the standard sizes offered by your printer. The closest standard sizes (5" × 8", 5.5" × 8.5", 6" × 9") match the industry perfectly.
Quick answers to the most common questions about book sizes and trim dimensions.
The most common book size for self-publishing is 5" × 8" (127 × 203mm), also called a small trade paperback. It's the default on Amazon KDP and IngramSpark, and works beautifully for fiction and general non-fiction. The second most popular is 5.5" × 8.5", which is the go-to for literary fiction, memoir, and business books.
For your first book, 5.5" × 8.5" is the safest all-around choice. It works for both fiction and non-fiction, looks professional, and keeps printing costs reasonable. If you're writing genre fiction (romance, thriller, mystery), go with 5" × 8" instead — it's what readers in those genres expect.
Yes, but it's not trivial. Changing your trim size means reformatting your entire interior PDF, redesigning your cover (since the spine width and dimensions change), and getting a new ISBN. On Books.by, you can upload new files anytime, but you'll want to order fresh proof copies before going live. It's much easier to get the size right from the start.
Amazon KDP supports trim sizes from 5" × 8" to 8.5" × 11" for paperback (they don't offer mass market 4.25" × 6.87"). IngramSpark offers a wider range, including mass market through large format. Books.by supports 13+ sizes including all the most popular options from both platforms, plus square and landscape formats. Your existing KDP or IngramSpark files will work directly on Books.by.
Indirectly, yes. Your trim size affects page count, which affects printing cost, which affects your per-sale royalty. A larger trim size means fewer pages for the same content, which can reduce printing costs. However, larger books also weigh more, increasing shipping costs. On Books.by, you keep 100% of the margin between your retail price and the printing cost. Use the royalty calculator to model different scenarios.
Trim size is the final dimensions of the printed, cut book — what the reader holds in their hand. Page size (or document size) is the dimensions of your PDF file. If your book uses bleed (images that extend to the edge), your page size will be 0.25" wider and 0.25" taller than the trim size (0.125" bleed on each side). If you don't use bleed, page size and trim size are the same.
Use whatever your printer requires. Most US-based POD services (Books.by, Amazon KDP, IngramSpark) list sizes in inches. International printers often use millimetres. Books.by accepts files formatted in either system. When in doubt, use the inch-based dimension names (5×8, 6×9) since they're universally understood in the self-publishing community.
Hardcover (case laminate) books use the same interior trim sizes as paperbacks. The cover boards extend slightly beyond the pages (called "overhang" or "boards"), typically about 0.125" on each side. So a 6" × 9" hardcover's interior pages are 6" × 9", but the overall cover dimensions are slightly larger. Books.by is adding hardcover support in 2026, with multiple trim sizes planned — the most popular hardcover sizes are 5.5" × 8.5" and 6" × 9".
Ebooks don't have a fixed trim size — the text reflows to fit whatever device the reader uses (phone, tablet, e-reader). Trim size only applies to print books. However, if you're creating a fixed-layout ebook (common for children's books, cookbooks, or heavily designed books), the layout dimensions should match your intended reading device. For reflowable ebooks on Books.by, just upload your EPUB file and it adapts automatically.
Books.by supports all standard trim sizes with global print-on-demand fulfillment. Upload your files, set your price, and start selling — all for $99/year.
