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KDP Cover Calculator UK | Amazon Book Cover Size & Spine Calculator 2025

Free Amazon KDP cover calculator for UK self-publishers. Calculate exact book cover dimensions, spine width, bleed areas and full wrap cover size. Updated 2026.

Last updated: February 2026

KDP Cover Calculator

Calculate exact Amazon KDP book cover dimensions, spine width and full wrap cover size for UK self-publishers

Standard Paperback Cover Calculator

5" × 8"
127 × 203 mm
5.5" × 8.5"
140 × 216 mm
6" × 9"
152 × 229 mm
5.25" × 8"
133 × 203 mm
7" × 10"
178 × 254 mm
8.5" × 11"
216 × 280 mm
Minimum 24 pages, maximum 828 pages for paperback

Hardcover (Case Laminate) Calculator

Hardcover: minimum 75 pages, maximum 550 pages

Quick Spine Width Calculator

Custom Size Calculator

Amazon KDP Spine Width Formulas

Use these official Amazon KDP formulas to calculate spine width:

Paper Type Formula (inches) Thickness per Page Min Pages for Spine Text
White Paper Pages × 0.0025" 0.0025 inches (0.0635 mm) 79 pages minimum
Cream Paper Pages × 0.0030" 0.0030 inches (0.0762 mm) 75 pages minimum
Colour Interior Pages × 0.0035" 0.0035 inches (0.0889 mm) 66 pages minimum
Important: Spine text is only allowed when the spine width is at least 0.2" (5.08mm). Books with fewer pages should have a blank spine.

Popular KDP Trim Sizes for UK Authors

Trim Size Metric (mm) Best For UK Equivalent
5" × 8" 127 × 203 mm Fiction, Novels, Poetry Similar to B-format
5.5" × 8.5" 140 × 216 mm Fiction, Memoirs Digest size
6" × 9" 152 × 229 mm Non-fiction, Business, Self-help Trade paperback
5.06" × 7.81" 129 × 198 mm Mass market fiction A-format equivalent
5.25" × 8" 133 × 203 mm Standard fiction Compact trade
7" × 10" 178 × 254 mm Textbooks, Cookbooks Large format
8.5" × 11" 216 × 280 mm Workbooks, Colouring books Letter size
8" × 10" 203 × 254 mm Children's books, Photography Large illustrated

KDP Cover Design Tips

  • Always use 300 DPI - Lower resolution will appear blurry when printed
  • Design in CMYK colour mode - RGB colours will shift when printed
  • Keep text 0.25" from edges - This is your "safe zone" to avoid cutting
  • Extend images to bleed - Artwork must go 0.125" past the trim line
  • Use PDF/X-1a:2001 format - This ensures best print quality
  • Check spine alignment - Centre spine text carefully, KDP is strict
  • Include barcode area - Leave space on back cover for ISBN barcode
  • Test with a proof copy - Always order a proof before publishing

Common KDP Cover Mistakes to Avoid

  • Wrong spine calculation - Using the wrong paper thickness formula
  • Text too close to spine - Text hidden in binding or cut off
  • Missing bleed - White edges appear on printed book
  • Low resolution images - Pixelated or blurry cover artwork
  • RGB colour mode - Colours look different when printed
  • Spine text on thin books - Adding text when spine is too narrow
  • Wrong file dimensions - Cover rejected by KDP system
  • Copyrighted images - Using images without proper licensing

Frequently Asked Questions

How do I calculate my KDP book spine width? +
Amazon KDP spine width depends on page count and paper type. For white paper: pages × 0.0025 inches. For cream paper: pages × 0.0030 inches. For colour interior: pages × 0.0035 inches. Our calculator automatically determines the correct formula based on your selections. A 200-page book on white paper would have a spine of 0.5 inches (12.7mm).
What is the standard bleed for KDP covers? +
Amazon KDP requires 0.125 inches (3.175mm) bleed on all sides of your cover. This means your artwork must extend 0.125 inches beyond the trim line on all edges to ensure clean printing without white borders. The bleed area will be trimmed off during production.
What are the most popular KDP trim sizes in the UK? +
The most popular trim sizes for UK authors are: 5×8 inches (127×203mm) for fiction, 6×9 inches (152×229mm) for non-fiction and business books, 8.5×11 inches (216×280mm) for workbooks and textbooks, and 5.5×8.5 inches (140×216mm) for premium paperbacks.
What resolution should my KDP cover be? +
Amazon KDP requires a minimum resolution of 300 DPI (dots per inch) for print covers. Your cover file should be saved as PDF (preferred), TIFF, or JPEG format. Our calculator shows the pixel dimensions needed at 300 DPI. Lower resolution will result in blurry or pixelated prints.
What is the safe zone on a KDP cover? +
The safe zone is the area where important text and images should be placed. Keep critical content at least 0.25 inches (6.35mm) from the trim edge and spine edge. This prevents text being cut off or hidden in the binding. The safe zone ensures your content remains visible after trimming.
How many pages minimum for spine text on KDP? +
Amazon KDP allows spine text for books with 79+ pages on white paper, 75+ pages on cream paper, or 66+ pages on colour paper. These thresholds result in a spine width of approximately 0.2 inches (5.08mm). Below these thresholds, you should leave the spine blank.
What file format should I use for my KDP cover? +
Amazon KDP accepts PDF (recommended), TIFF, PNG, and JPEG formats for covers. PDF preserves quality best and supports CMYK colour mode. File size limit is 650MB. Use PDF/X-1a:2001 format for professional results. Avoid compressed JPEG for final files.
Can I use RGB colour mode for KDP covers? +
While Amazon KDP accepts RGB files, they will convert them to CMYK for printing. This can cause colour shifts, especially in bright blues, greens, and oranges. For accurate colours, design in CMYK mode from the start using a print colour profile like US Web Coated (SWOP) v2.

UK Self-Publishing Resources

Amazon KDP Help

Official KDP documentation for cover formatting and specifications

Alliance of Independent Authors

UK-based organisation for self-published authors

Writers & Artists

Bloomsbury resource for UK writers and self-publishers

Nielsen ISBN Agency UK

Official UK ISBN registration for self-publishers

About the KDP Cover Calculator

Our free Amazon KDP Cover Calculator helps UK self-publishers and authors create perfectly sized book covers for Kindle Direct Publishing. Whether you're publishing your first novel, a business book, or a children's colouring book, getting the cover dimensions exactly right is crucial for a professional result.

This calculator uses Amazon's official formulas to determine spine width based on page count and paper type. It automatically calculates the full cover width (including bleed areas), the safe zone for text placement, and provides pixel dimensions at 300 DPI for design software like Adobe Photoshop, Canva, or GIMP.

UK-specific features: All measurements are shown in both imperial (inches) and metric (millimetres) units. We include UK trim size equivalents and resources specifically for British self-publishers, including the Nielsen ISBN Agency UK and Alliance of Independent Authors.

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Expert Reviewed — This calculator is reviewed by our team of financial experts and updated regularly with the latest UK tax rates and regulations. Last verified: February 2026.

Last updated: February 2026 | Verified with latest UK rates

Pro Tips for Accurate Results
  • Double-check your input values before calculating
  • Use the correct unit format (metric or imperial)
  • For complex calculations, break them into smaller steps
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Understanding Your Results

Our Kdp Cover Calculator provides:

  • Instant calculations - Results appear immediately
  • Accurate formulas - Based on official UK standards
  • Clear explanations - Understand how results are derived
  • 2025/26 updated - Using current rates and regulations
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Professional Advice: Getting Your KDP Cover Print-Ready

After calculating your cover dimensions, ensure your design file meets Amazon KDP's technical specifications for successful printing. Your cover image must be submitted as a PDF at 300 DPI resolution, with all text and critical elements placed at least 3.2 millimetres inside the trim line to avoid being cut off during production. The bleed area, which extends 3.2 millimetres beyond each edge, should contain only background colour or imagery that can be safely trimmed. For the spine, avoid placing text if your book has fewer than 79 pages for white paper or 40 pages for cream paper, as thin spines can cause text misalignment during binding. Use CMYK colour mode rather than RGB, as screen colours may appear different when printed. Free tools like Canva and GIMP can produce acceptable results, but professional designers often use Adobe InDesign or Affinity Publisher for precise control over bleed, margins, and colour profiles.

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