Tools & Software

KDP Trim Size Guide — Find the Perfect Size for Your Book

TL;DR

Pick the right KDP paperback or hardcover trim size for your genre, page count and intended retail price. Covers all KDP-supported sizes from 5x8 mass-market through 8.5x11 letter, with genre conventions and the impact each trim has on spine width, royalty and printing cost.

Find the perfect trim size for your Amazon KDP paperback. Use the genre selector below to see recommended sizes, or browse the complete filterable table of all available KDP trim sizes.

Choose Your Genre

Click a genre to see the recommended trim sizes and UK publishing conventions:

Fiction / Novels

5" x 8", 5.25" x 8", 5.5" x 8.5", 6" x 9"
UK B-format equivalent: 5.5" x 8.5"

Non-Fiction / Self-Help

5.5" x 8.5", 6" x 9", 7" x 10"
UK Royal format equivalent: 6.14" x 9.21"

Memoir / Biography

5.5" x 8.5", 6" x 9"
UK Demy format equivalent: 5.5" x 8.5"

Children's Books

8.5" x 8.5", 8.25" x 8.25", 8.5" x 11"
Square formats popular for picture books

Poetry

5" x 8", 5.25" x 8", 5.5" x 8.5"
Smaller sizes suit the intimate feel of poetry

Textbooks / Workbooks

7" x 10", 8" x 10", 8.5" x 11"
Larger sizes for tables, diagrams, and exercises

Photography / Art Books

8.5" x 8.5", 8" x 10", 8.5" x 11"
Bleed required for full-page images

Romance

5" x 8", 5.25" x 8", 5.5" x 8.5"
Mass-market feel: 5" x 8" is closest to UK A-format

Visual Size Comparison

Sizes shown at relative scale. Click a genre above to highlight recommended sizes.

Complete KDP Trim Size Table

Filter and search all available Amazon KDP trim sizes:

Trim Size (in)Metric (mm)BleedNo-BleedBest ForNotes

UK Publishing Size Equivalents

For UK authors, here is how traditional British book formats map to KDP trim sizes:

UK FormatUK Size (mm)Closest KDP SizeKDP Size (mm)
A-format (mass market)110 x 1785" x 8"127 x 203
B-format (standard)129 x 1985.25" x 8" or 5.5" x 8.5"133 x 203 or 140 x 216
C-format (trade)135 x 2165.5" x 8.5"140 x 216
Demy138 x 2165.5" x 8.5"140 x 216
Royal156 x 2346.14" x 9.21"156 x 234
Crown Quarto189 x 2467.44" x 9.69"189 x 246

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Frequently asked questions

Which KDP trim size matches the UK B-format paperback?

The closest KDP equivalent to the UK B-format (129 x 198 mm) is 5.25" x 8" (133 x 203 mm) or 5.5" x 8.5" (140 x 216 mm). KDP also offers an exact 5.06" x 7.81" option that matches B-format precisely.

What trim size should I use for a children's picture book?

Square sizes like 8.25" x 8.25" or 8.5" x 8.5" suit picture books, and 8.5" x 11" works for larger illustrated titles. Bleed should be enabled so full-page illustrations extend to the trimmed edge.

Which KDP trim size is closest to the UK Royal format?

KDP's 6.14" x 9.21" (156 x 234 mm) is an exact match for the UK Royal format. It is a common choice for non-fiction and academic titles.

Can I change a KDP book's trim size after publishing?

No — trim size is locked once a book is live. To change it you have to unpublish the title, create a new edition at the new trim size, and republish with a new ISBN.

Not sure which size to pick?

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Robert Prime

The publishing.co.uk Team

Robert Prime is a best-selling self-published author, veteran eCommerce strategist, and the founder of publishing.co.uk.

Robert Prime — Founder of publishing.co.uk

About the Author

Robert Prime

Robert Prime is a best-selling self-published author, veteran eCommerce strategist, and the founder of publishing.co.uk. With over 25 years of experience in digital business he brings a battle-tested perspective to the publishing industry. After experiencing firsthand the archaic, headache-inducing process of formatting a KDP-compliant book for his own best-seller, Google. Panic. Repeat., Robert built publishing.co.uk to solve the problem for other authors. He is also a co-owner of the LoveReading.co.uk network (the UK's leading book discovery platforms), founder of the Amazon growth agency MrPrime.com, and a member of the Forbes Business Council.

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