Book Trim Sizes: What to Choose, in Inches and Centimetres

The Sizes You’ll Actually Meet

Publishing has no standards body that decides these. The names below are trade habits, and printers round them differently, so treat the figures as what you’ll commonly see quoted.

Name	Inches	Centimetres	Usually
US mass market, “pocket”	4.25 x 6.87	10.8 x 17.45	Small paperbacks on grocery-store racks
UK A-format	4.4 x 7	11.1 x 17.8	Mass-market fiction
UK B-format	5.1 x 7.8	12.9 x 19.8	The UK fiction paperback
US “novel”	5 x 8	12.7 x 20.32	Fiction, popular with self-publishers
	5.25 x 8	13.34 x 20.32	Fiction, memoir
Digest	5.5 x 8.5	13.97 x 21.59	Fiction, memoir, non-fiction
Demy	5.4 x 8.5	13.8 x 21.6	UK memoir, biography, trade non-fiction
A5	5.83 x 8.27	14.8 x 21	Non-fiction, manuals, journals, poetry
Trade, “US Royal”	6 x 9	15.24 x 22.86	US trade paperbacks and hardcovers
Royal	6.14 x 9.21	15.6 x 23.4	Textbooks, business, reference
	7 x 10	17.78 x 25.4	Textbooks, non-fiction
	8.5 x 11	21.59 x 27.94	Textbooks

The UK names and uses follow Imprint’s trim-size chart, a British printer’s guide. The US names follow Reedsy’s guide. Note that “B-format” means something else again if an American printer says it.

What Each Kind of Book Tends to Use

These are habits, and you’ll find exceptions on any shelf.

Novels. Reedsy’s guide lists 4.25 x 6.87, 5 x 8, 5.25 x 8, 5.5 x 8.5 and 6 x 9 for fiction. The small end isn’t on KDP’s list, though a custom size can reach it, as below. A novel at 5 x 8 feels like a novel. It also holds fewer words a page, so a book that runs 320 pages at one size can run noticeably longer at a smaller one.

Long fantasy and science fiction. A 200,000-word book at 5 x 8 has a spine you could stand a mug on. Going up to 6 x 9 cuts the page count, which helps with both printing cost and KDP’s page limit, though a large page of dense text is its own kind of commitment for the reader.

Memoir. Reedsy suggests 5.25 x 8 or 5.5 x 8.5. Imprint lists Demy for memoir and biography in the UK.

Non-fiction. 5.5 x 8.5, 6 x 9 or 7 x 10, according to Reedsy, with the larger sizes suiting books with tables, diagrams or exercises. A book meant to be scribbled in wants room for scribbling.

Hardcover. At KDP you get five sizes and that’s it, so a hardcover of your novel may need to match one of them.

KDP’s Paperback Sizes

KDP lists these for its main site (kdp.amazon.com), which also serves European marketplaces. All are width by height.

Inches	Centimetres	Black ink, white paper	Large trim
5 x 8	12.7 x 20.32	24 to 828 pages	No
5.06 x 7.81	12.85 x 19.84	24 to 828	No
5.25 x 8	13.34 x 20.32	24 to 828	No
5.5 x 8.5	13.97 x 21.59	24 to 828	No
6 x 9	15.24 x 22.86	24 to 828	No
6.14 x 9.21	15.6 x 23.39	24 to 828	Yes
6.69 x 9.61	16.99 x 24.41	24 to 828	Yes
7 x 10	17.78 x 25.4	24 to 828	Yes
7.44 x 9.69	18.9 x 24.61	24 to 828	Yes
7.5 x 9.25	19.05 x 23.5	24 to 828	Yes
8 x 10	20.32 x 25.4	24 to 828	Yes
8.25 x 6	20.96 x 15.24	24 to 800	Yes
8.25 x 8.25	20.96 x 20.96	24 to 800	Yes
8.27 x 11.69	21 x 29.7	24 to 780	Yes
8.5 x 8.5	21.59 x 21.59	24 to 590	Yes
8.5 x 11	21.59 x 27.94	24 to 590	Yes

Cream paper is thicker and lowers the maximums: 776 pages at most sizes, with lower figures at the largest. Groundwood paper’s maximum is 812 at most sizes. Standard colour runs from 72 to 600 pages and isn’t offered at 8.27 x 11.69.

KDP also takes a custom paperback size: anything from 4 to 8.5 inches wide (10.16 to 21.59 cm) and 6 to 11.69 inches tall (15.24 to 29.69 cm). That’s how you’d print a true A5 or a mass-market size through KDP, since neither is on the list for this site. A5 appears only among the sizes for KDP’s Japanese site. UK B-format doesn’t need it: 5.06 x 7.81 inches is within a millimetre. KDP’s help doesn’t say on the pages we read whether a custom size stays eligible for its Expanded Distribution, whose eligibility chart does vary by size, so check that chart first if bookshops matter to you.

KDP’s Hardcover Sizes

Five, all from 75 to 550 pages:

Inches	Centimetres	Large trim
5.5 x 8.5	13.97 x 21.59	No
6 x 9	15.24 x 22.86	No
6.14 x 9.21	15.6 x 23.39	Yes
7 x 10	17.78 x 25.4	Yes
8.25 x 11	20.96 x 27.94	Yes

KDP hardcovers are case laminate, with the art printed on the cover and no dust jacket, and Expanded Distribution doesn’t cover them.

Choosing Without Overthinking It

Pull three books from the shelf where yours would sit, the ones you’d be glad to be mistaken for, and get a ruler. That’s the research. Everything else is arithmetic.

Then do the arithmetic. A bigger page holds more words, so it means fewer pages, which lowers per-page printing cost but may tip you into large trim if you go past 6.12 inches wide or 9 tall. KDP’s printing cost is a fixed cost plus a charge per page, and it comes out of your royalty, so on a long novel it’s worth running your real page count through the sums for two sizes before deciding.

Settle it early, because trim size is the first domino. It sets the page count, which sets the gutter and the spine width, which sets the cover. Changing your mind after the cover is designed costs a good deal more than the ruler did.

Shiro’s Publish lens offers 5 x 8, 5.25 x 8, 5.5 x 8.5, 6 x 9, 6.14 x 9.21 and A5, and checks your page count against KDP’s limits. Changing your mind there means picking another size and exporting again, which you will.

Sources

Read in November 2026: KDP’s print options, trim size, bleed and margins, hardcover and Expanded Distribution pages; Imprint; Reedsy. KDP’s figures can change, so confirm them on its site before you commit.

The Questions People Ask

What is the standard book size for a novel?

There’s no single standard. In the US, 5 x 8, 5.5 x 8.5 and 6 x 9 inches are the usual trade sizes. In the UK, B-format at 129 x 198 mm is the common fiction paperback. KDP calls 6 x 9 the most common US trim size overall, across all kinds of book.

What is the difference between trim size and page size?

Trim size is the finished book’s width and height. Page size is the page in your file. They’re the same unless your book has bleed, in which case KDP wants the file 0.125 inch wider and 0.25 inch taller than the trim.

Does trim size change how much a book costs to print?

Yes, in two ways. A smaller page means more pages, and printing is charged partly by the page. And at KDP, a book wider than 6.12 inches or taller than 9 inches is large trim, which has its own printing cost.

Can I change the trim size after publishing?

Plan as if you can’t. Changing trim size reflows the whole interior, changes the page count and the spine, and means a new cover file. KDP locks ink type after publication, and the pages we read don’t cover trim size, so check its current rules or ask its support before changing a live book.

Last revised November 2026.