Ultimate Guide to Hardback and Paperback Book Sizes in 2025
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Contents Table:
What Are the Standard Book Sizes in Publishing?
Measuring Book Dimensions for Publishing
Standard Book Sizes in the UK
B-Format Trim Size
A5 Book Trim Size
Royal Trim Size
Book Trim Sizes by Genre
Mass Market vs. Trade Book Sizes
Paperback vs Hardback Book Sizes
What is a Paperback Book?
What is a Hardback Book?
Hardback vs Paperback Book Sizes UK
Global Differences in Standard Book Sizes
Print-on-Demand Book Dimensions for Publishing
Choosing the Right Book Size for Your Next Project
Standard Book Sizes in Publishing FAQs
What are standard UK book sizes?
What are standard book sizes?
Are novels A5 or A6?
What size is a children’s book?
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Choosing the right book sizes isn’t just about aesthetics. How you publish your book affects everything from reader experience to production costs, and there are standards across genres that can help set reader expectations.
Not sure where to start? We can help.
Drawing on our years of experience as book publishers, we’ve put together everything you need to know about standard book sizes in the UK.
Learn more about genre formats, book trim sizes, and hardback vs paperback options to make the right decision for your self-published book.
Measuring Book Dimensions for Publishing
Before you dive into choosing a size, it’s helpful to understand how books are measured:
- Cover Dimensions: The height and width of your book’s cover are the primary measurements.
- Spine Thickness: This indicates how thick your book is and is typically measured in millimetres for accuracy.
- Trim Size: This is the final size of your book after it’s been bound and trimmed.
When we talk about choosing a book size, this refers to trim size only.
Standard Book Sizes in the UK
There’s a range of book size standards used in self-publishing.
Learning the names of different sizes and what they’re used for is a great first step to finding the right measurements for your book.
In UK bookshops, you’ll tend to find the following trim sizes:
B-Format Trim Size
The B-format is widely used in the UK and is a standard for paperbacks. It’ll give your book a traditional “bookshop novel” look that many self-publishers love.
If you’re aiming for a professional aesthetic similar to books found in major retailers, B-format is a strong choice.
A5 Book Trim Size
A5 is another common trim size for paperback books. It’s portable, compact, and feels familiar to readers, though it’s slightly larger than a typical bookshop book.
Royal Trim Size
The Royal book trim size is the largest of the three, lending a more impactful and premium feel to books.
It’s popular amongst both fiction and non-fiction titles and allows for more generous margins and an uncluttered layout.
In self-publishing, it’s typically used for short-run book printing where price-per-copy is less of a concern.
Book Trim Sizes by Genre
When exploring the best size for a self-published book, you might want to choose a standard trim size based on your genre.
Take a look at our book size guide to learn more about typical UK standards:
| Book Genre | Trim Size |
| Fiction |
|
| Non-fiction |
|
| Children’s books (0-2 year olds) | 190 x 190mm (7.5 x 7.5 inches) |
| Children’s books (2-5 year olds) | 178 x 25mm (7 x 10 inches) |
| Children’s books (5+ year olds) | 254 x 203 mm (10 x 8 inches) |
| Photo books | B5: 250 x 175mm (9.84 x 6.88 inches) |
| Comic books | 257 x 168mm (10.11 x 6.61 inches) |
| Pocketbook s |
|
| Workbooks | 203 x 254mm (8 x 10 inches) |
| Coffee table books |
|
While these are standards, there’s no set rule for print-on-demand book sizes, especially when self-publishing.
If you want to make a coffee table book that’s 400mm x 100mm, you can!
By opting for the self-publishing route, you have creative freedom on how your book looks when printed, including its trim size.
CTA: To learn more about your book sizing options, request a free sample from our trusted book printers.
Mass Market vs. Trade Book Sizes
Trade books refer to books printed by commercial publishers. These include both paperbacks and hardcovers, and they are the standards that you commonly find in bookshops. They can come in a range of sizes (as shown in the chart below) but are typically either B-format, A5, or Royal.
Mass market paperbacks are a smaller, more affordable type of book compared to trade books. These prints use cheaper paper and simpler cover finishes to keep production costs low, and are typically printed in large quantities ranging from thousands to hundreds of thousands of copies.
| Book Format | Common Book Sizes |
| Mass market books | 108 x 175mm (4.25 x 6.87 inches) |
| Trade books |
|
CTA: Unsure whether trade or mass market printing is best for your budget? Request a custom book printing quote to explore the best trim size options for your project.
Paperback vs Hardback Book Sizes
Paperbacks and hardbacks can differ in trim sizes. If you’re not sure which format to choose for your self-published book, we’ve compared the two:
What is a Paperback Book?
Paperback books have soft covers made of thick paper. They’re often cheaper to print than hardback books, making them more accessible to a wider audience of self-publishers and readers.
What is a Hardback Book?
Hardback book printing uses harder covers made of sturdy binder’s board.
In commercial fiction publishing, authors often release novels first as a hardback and later as a paperback. This is largely because hardbacks can sell at a higher profit margin, helping publishers recoup their investment quickly.
You’ll also find hardbacks are a popular option for photobooks, non-fiction books, and children’s books.
Hardback vs Paperback Book Sizes UK
Hardback books tend to be larger than standard paperback book sizes in both trim size and spine thickness.
This, alongside the materials used for the harder covers, makes them a more expensive option when self-publishing.
| Book Format | Book Size Measurements |
| Paperback books | B-Format, A5, 152 x 229mm |
| Hardback books | 152 x 229mm (6 x 9 inches) to 216 x 279mm (8.5 x 11 inches) |
Global Differences in Standard Book Sizes
Standard book sizes will vary depending on the country you’re publishing in. For example, when it comes to the standard fiction trim size of A5 vs B-format books, the UK and the US differ.
The US doesn’t commonly use A5 when publishing. Instead, they use a B format that’s very slightly smaller than the UK equivalent.
| Region | Book Format | Book Size Range |
| UK | B-Format Books |
|
| US | B-Format Books |
|
Important note: These differences, though subtle, can impact your book’s market appeal and compatibility, especially when distributing internationally..
Print-on-Demand Book Dimensions for Publishing
Print-on-demand is a popular option when self-publishing. Here’s a snapshot of the standard book sizes offered by some of the major players:
| Print-on-Demand Provider | Standard Book Sizes Available |
| Createspace/KDP |
|
| Blurb photobooks |
|
| Shutterfly |
|
Choosing the Right Book Size for Your Next Project
By using the standard book sizes and formats covered in this guide, you can find a size that works for you. Whether you’re working on a novel, memoir, photobook or children’s story, the right size will shape how your book looks and feels in a reader’s hands.
CTA: For your next project, request a free sample or use our instant price calculator to find out how much your hardback or paperback books will cost to print.
Standard Book Sizes in Publishing FAQs
What are standard UK book sizes?
Book trim sizes in the UK vary depending on whether you opt for a hardcover or softcover book, and the genre of book you’re publishing.
For paperback fiction books, for instance, it’s standard to choose from either an A5 or B-format.
If you’re publishing a book for children aged 2 or under, 190 x 190mm (7.5 x 7.5 inches) is a common choice.
What are standard book sizes?
Standard book trim sizes include:
| Trim Size | Dimensions (mm) | Common Uses |
| B-Format | 198 x 129 or 210 x 135 | Fiction, paperbacks |
| A5 | 210 x 148 | Fiction, memoirs, workbooks |
| Trade Paperback | 229 x 152 | Non-fiction, literary fiction |
| Mass Market Paperback | 108 x 175 | Budget fiction, genre series |
| Royal | 234 x 156 | Non-fiction, hardbacks, memoirs |
| A4 | 297 x 210 | Workbooks, manuals, portfolios |
These are used for different genres of books. For example, Royal trim sizing is common for hardback books, while B-format is typically used for paperback books.
Are novels A5 or A6?
Paperback novels tend to be A5 rather than A6, with dimensions of 210 x 148mm (8.26 x 5.82 inches). A6 is more frequently used for pocketbooks, booklets, and maps, where portability is a crucial selling point. A6 pocketbooks have dimensions of 105 x 74mm (4.13 x 2.91 inches).
What size is a children’s book?
Children’s books come in a wide variety of sizes, with less of a common standard than adult fiction and non-fiction books. You can find children’s books that are very small, with board books for newborns typically measuring 6 x 6 inches, as well as much larger picture books measuring 10 x 10 inches.
Choose your children’s book size based on the age of your target reader and the purpose of your book.
