KDP Trim Sizes Explained: Which Size is Right for Your Book?

Choosing the right trim size for your KDP book is more important than you might think. The size affects not just production costs but also reader perception, genre fit, and even your book's shelf appeal.

Why Trim Size Matters

Your book's trim size (the final dimensions after cutting) impacts:

• Printing costs: Larger books cost more to print
• Reader expectations: Each genre has standard sizes readers expect
• Shelf presence: Size affects how your book looks in bookstores
• Shipping costs: Larger dimensions = higher shipping fees
• Page count perception: Same content in different sizes creates different page counts

All 16 KDP Paperback Trim Sizes

Amazon KDP offers these paperback trim sizes. Here's what you need to know about each:

Standard Sizes

• 5×8": Compact and portable, great for mass-market feel
• 5.5×8.5": Popular for memoirs and smaller books
• 6×9": ⭐ Most popular – perfect for novels, memoirs, non-fiction
• 7×10": Larger format for textbooks and technical books
• 8.5×11": Standard letter size for workbooks and journals

International Sizes

• 5.06×7.81": European B-format (129×198mm)
• 6.14×9.21": European standard (156×234mm)
• 8.27×11.69": A4 size, common in Europe and Asia

Specialty Sizes

• 5.25×8": Slightly wider than 5×8", unique positioning
• 6.69×9.61": European Großformat
• 7.44×9.69": Another European option
• 7.5×9.25": Between standard 6×9 and 8.5×11
• 8×10": Square-ish format for photo books
• 8.25×6": Landscape orientation
• 8.25×8.25": Square format for children's books
• 8.5×8.5": Larger square format

Choosing by Genre

Different genres have different reader expectations. Using the "wrong" size can make your book look unprofessional:

Fiction

• Literary fiction: 5.5×8.5" or 6×9"
• Thrillers/Mystery: 6×9" (industry standard)
• Romance: 5×8" or 5.5×8.5" (mass-market feel)
• Science Fiction/Fantasy: 6×9"
• Horror: 5.5×8.5" or 6×9"

Non-Fiction

• Business books: 6×9" (professional standard)
• Self-help: 5.5×8.5" or 6×9"
• How-to guides: 7×10" or 8.5×11" (room for diagrams)
• Cookbooks: 8.5×11" (space for photos)
• Technical/Academic: 7×10" or 8.5×11"
• Biography/Memoir: 6×9"

Children's Books

• Picture books: 8.5×8.5" or 8.5×11"
• Early readers: 6×9" or 7×10"
• Middle grade: 5.5×8.5" or 6×9"
• Young adult: 5.5×8.5" or 6×9"

Hardcover Sizes (5 Options)

KDP offers 5 hardcover trim sizes:

• 5.5×8.5"
• 6×9" ⭐ Most popular
• 6.14×9.21" (European standard)
• 7×10"
• 8.25×11"

Hardcovers are premium products. The 6×9" size works for most books, while 7×10" and 8.5×11" are better for illustrated or coffee table books.

Cost Considerations

Trim size directly affects your printing costs and profit margins:

Printing Cost Formula

Amazon charges: Base cost + (page count × $0.012 for black & white) × size multiplier

• 5×8" to 6×9": Standard multiplier (1.0×)
• 6.14×9.21" to 7×10": Medium multiplier (~1.15×)
• 8.5×11": Highest multiplier (~1.4×)

Example: 200-Page Book

• 5×8": ~$3.50
• 6×9": ~$3.65
• 7×10": ~$4.20
• 8.5×11": ~$4.50

That $1 difference might seem small, but if you sell 1,000 copies, it's $1,000 in extra costs eating into your profits.

Page Count Impact

The same content creates different page counts in different sizes. A 50,000-word novel might be:

• 250 pages at 5×8"
• 200 pages at 6×9"
• 150 pages at 8.5×11"

Psychological impact: A 150-page book might seem "too short" for a novel, while 250 pages feels substantial. Consider reader perception when choosing size.

Professional Appearance

Your trim size should match industry standards for your genre. Using an unusual size can make your book stand out—but not always in a good way.

When to Use Standard Sizes (6×9", 5.5×8.5")

• First-time authors establishing credibility
• Genre fiction following market norms
• Books targeting traditional bookstore placement
• Maximizing profit margins

When to Use Unique Sizes

• Children's books (square formats work great)
• Coffee table books (large formats showcase images)
• Workbooks and journals (8.5×11" provides writing space)
• International markets (using local standard sizes)

Spine Width Considerations

Trim size affects spine width calculation. For books under 79 pages, KDP doesn't allow spine text regardless of trim size. For thicker books:

• Wider trim sizes create wider spines at the same page count
• More spine space means easier-to-read spine text
• Consider spine visibility on bookstore shelves

Learn more: Understanding KDP Spine Width

Making Your Decision

Follow this decision framework:

1. Research your genre: What do bestsellers in your category use?
2. Consider your content: Images? Diagrams? Lots of white space?
3. Calculate costs: How does size affect your profit per sale?
4. Think about readers: What size will they expect and prefer?
5. Test if possible: Order proof copies in different sizes