What File Format Does KDP Accept? Complete Guide

By Robert Prime

Last reviewed by Robert Prime — March 2026

Table of Contents

• Introduction: Why KDP File Formats Matter
• What You Need to Know Before Starting
• Step-by-Step Guide to Preparing Your KDP Files
• Common Terminology and Definitions
• UK-Specific Considerations for KDP File Formats
• Common Mistakes and How to Avoid Them
• Tools and Resources for UK Authors
• Cost Breakdown: What UK Authors Should Budget For
• Expert Tips from 25 Years in the Industry
• Real-World Case Studies and Examples
• Comparison with Alternative Publishing Approaches
• Frequently Asked Questions

Introduction: Why KDP File Formats Matter

If you’re an author self-publishing through Amazon’s Kindle Direct Publishing (KDP) platform in the UK, understanding the right file formats is not just a technical necessity—it’s a commercial imperative. The file format you submit affects everything from how your book appears on Kindle devices and in print to your sales potential.

From my 25 years navigating e-commerce and Amazon marketplaces, I’ve learned that many UK authors underestimate this step. When I wrote Google. Panic. Repeat., the formatting nightmare was on a different level. Despite my technical background, getting the manuscript into a KDP-ready format cost me hours of frustration and wasted money on inadequate freelancers.

Before building publishing.co.uk, I hired a so-called ’expert’ formatter for £130 who delivered a mess—missing chapters, broken TOCs, and inconsistent fonts. Fiverr gigs were no better, and the automated tools available at the time were awful. This experience shaped how I approach formatting advice today: practical, UK-focused, and no-nonsense.

This guide is designed to be your definitive UK-focused resource on KDP file formats. It goes beyond the usual US-centric advice, offering practical, no-nonsense insights tailored to the British market, including cost breakdowns in GBP and tips from someone who’s been in the trenches.

Data visualisation showing UK self-publishing market growth and KDP’s share

What You Need to Know Before Starting

Before you start converting your manuscript into a KDP-compatible file, there are some fundamentals you need to grasp. KDP primarily caters to two types of publishing: ebooks (Kindle) and print books (paperback and hardcover). Each has specific file format requirements and quirks.

KDP’s Accepted File Formats

• For Kindle eBooks:

  • EPUB (.epub) — The modern standard Amazon now prefers.
  • MOBI (.mobi) — Legacy format, still accepted but deprecated.
  • DOC/DOCX (.doc, .docx) — Microsoft Word files, commonly used but riskier due to formatting inconsistencies.
  • HTML (.html, .htm) — For advanced users who want granular control.
  • RTF (.rtf) — Rich text format, less common.
  • Plain Text (.txt) — Last resort, minimal formatting.

• For Print Books:

  • PDF (.pdf) — The only accepted format for interior files for print.
  • DOC/DOCX (.doc, .docx) — Accepted but highly discouraged because of formatting inconsistencies and KDP’s conversion quirks. PDF is preferred.
  • JPEG/PNG (.jpg, .png) — For cover images only, not interiors.

Why Does File Format Matter?

The file format determines how your book renders on devices, the quality of your print, and crucially, your book’s readability and professional appearance. A badly formatted Kindle file can result in jarring line breaks, missing images, or broken tables of contents. For print, the wrong PDF settings can mean blurry images, incorrect margins, or bleed issues.

In the UK, where the market is competitive and discerning, these technical details can make or break your book’s success.

Step-by-Step Guide to Preparing Your KDP Files

Preparing files for KDP is more than uploading and hitting publish. Here’s a detailed process that I recommend, based on my experience and what I’ve seen fail with others.

Step 1: Manuscript Preparation

Use Microsoft Word or Google Docs to create your manuscript. These are the most common starting points in the UK market.

• Set your trim size early, e.g., 5” x 8” (127mm x 203mm) for paperbacks—a popular UK choice because it’s compact, reader-friendly, and widely accepted by retailers.
• Use Styles in Word (Heading 1, Normal, etc.) for chapter titles, body text, and subheadings. This ensures consistent formatting throughout your book and facilitates automatic generation of the table of contents.
• Avoid manual line breaks or tabs for indents. Use paragraph settings instead:
  Layout > Paragraph > Indentation > Special > First line. This prevents formatting disasters when converting to EPUB or PDF.
• Insert page breaks at the end of chapters (Insert > Page Break) to avoid flow issues when KDP converts your files.
• For non-fiction books, use numbered and bulleted lists sparingly and with consistent styles to ensure proper rendering.

Step 2: Formatting for Kindle eBook

• Export your manuscript as DOCX with clean styles. Avoid embedded fonts or unusual characters that Kindle devices might not support.
• Use Kindle Previewer (Amazon’s free downloadable tool) to check how your eBook will look on different Kindle devices and apps. Download from kdp.amazon.com/en_GB/help/topic/G202131170.
• Consider converting your DOCX to EPUB using professional tools like Calibre (free, Windows, Mac, Linux) or Vellum (Mac only, premium). Vellum is my personal favourite for producing flawless UK-ready EPUB files, but it carries a price tag. Calibre is excellent for budget-conscious authors but requires some learning.
• Validate your EPUB file with the official EPUB Validator (W3C) at validator.idpf.org to catch common errors that might cause Amazon to reject your upload or cause display issues.
• Add a hyperlinked table of contents using Word’s References > Table of Contents feature or through EPUB editing tools. KDP requires an active TOC for navigation on Kindle devices.
• Avoid complex layouts, multi-column text, and embedded fonts that Kindle doesn’t support—stick to simple, clean styles.

Step 3: Formatting for Print

• Format your manuscript in Word or Adobe InDesign using the exact trim size you plan to use. Common UK sizes include 5" x 8" (127mm x 203mm) and A5 (148mm x 210mm). Check KDP’s supported sizes at kdp.amazon.com/en_GB/help/topic/G201834340.
• Set margins with extra room for the gutter (binding edge):
  Layout > Margins > Custom Margins; add at least 0.125” (3mm) for the gutter. For books over 200 pages, increase the gutter margin accordingly.
• Use fonts that embed well in PDFs (e.g., Garamond, Baskerville, Georgia). Avoid overused, amateurish fonts like Papyrus or Bleeding Cowboys. Also, avoid system fonts like Calibri or Arial which may not embed consistently.
• Export to PDF using high-quality settings:
  File > Save As > PDF > Options > ISO 19005-1 compliant (PDF/A). This ensures fonts and images are embedded properly for print.
• Ensure images are at least 300 dpi for print quality, especially for illustrations, photos, or graphs.
• Check for bleed if images or backgrounds extend to the edge. Typically, add 0.125” (3mm) bleed on all sides. This is non-negotiable for print covers and any full-page images in the interior.
• Use Adobe Acrobat Pro or similar to check your PDF for embedded fonts and colour profiles before uploading.

Step 4: Cover File Preparation

• Cover files must be submitted as JPEG or TIFF for print; JPEG or PNG for Kindle eBooks.
• Follow KDP’s exact pixel dimensions based on trim size and page count. KDP’s Cover Calculator (kdp.amazon.com/en_GB/cover-calculator) is invaluable here. For example, a 200-page 5” x 8” paperback requires a cover image roughly 3300 x 2550 pixels at 300 dpi.
• Include barcode space for print covers; KDP can add the barcode for free if you leave the area blank or use their template. Many UK authors forget this and have to reupload covers.
• For UK print books, ensure your cover adheres to the EAN-13 barcode standard, which differs from US ISBN barcodes. KDP handles this automatically if you choose to have them assign the ISBN barcode.

Step 5: Upload and Preview

• Log in to your KDP account at kdp.amazon.co.uk to ensure the UK storefront and market preferences are active.
• Upload your files carefully, selecting the correct trim size, paper type (cream vs white), and cover finish (matte or glossy).
• Use KDP’s Print Previewer and Online Previewer to check your files visually. These tools simulate how your book will look on Kindle devices and in print.
• Download the preview files and review on multiple devices, including Kindle apps for iOS, Android, and physical Kindle devices if possible.
• Order a Print Proof Copy to physically inspect the print quality. This is vital and often overlooked by UK authors trying to cut costs—nothing beats holding your book in hand. Expect to pay between £5 and £15 depending on page count and paper type.

Common Terminology and Definitions

Understanding the jargon is crucial. Here are terms you need to know:

• EPUB: Electronic Publication, a reflowable eBook format compatible with most devices including Kindle (Amazon recently shifted to EPUB as preferred).
• MOBI: An older Kindle eBook format, replaced gradually by EPUB. Still accepted but not recommended.
• Trim Size: The final dimensions of your physical book (e.g., 5” x 8”). This affects layout and cover size. UK authors often choose 5” x 8” or A5.
• Bleed: Extra image area extending beyond the trim edge, ensuring no unprinted edges after trimming. Usually 3mm (0.125”) in the UK.
• Gutter: The inner margin where the book is bound; should be wider than outer margins to avoid text being swallowed. Critical for books thicker than ~150 pages.
• PDF/A: A PDF standard for archiving, ensuring fonts and images are embedded correctly for print.
• Amazon KDP Print Previewer: The tool that simulates how your print book will look once published.
• ISBN: International Standard Book Number, used for book identification. In the UK, ISBNs are purchased via Nielsen Book.
• EAN Barcode: European Article Number barcode standard used on print book covers in the UK.
• VAT (Value Added Tax): A UK tax affecting ebooks differently than print books. Print books are zero-rated; ebooks generally attract 20% VAT.
• Kindle Previewer: Amazon’s desktop app to preview ebook formatting on various Kindle devices.
• Styles: Predefined formatting options in Word for headings, body text, etc., used for consistent formatting and TOC generation.

UK-Specific Considerations for KDP File Formats

While much of Amazon KDP’s documentation is US-centric, UK authors face distinct challenges and opportunities.

ISBNs and Barcodes

Unlike the US, where Bowker issues ISBNs, UK authors must use Nielsen for UK ISBNs. As of 2026:

• Single ISBN: £93
• Block of 10 ISBNs: £174

Buying your own ISBNs is crucial in the UK because:

• Free Amazon ISBNs list Amazon as the publisher, which can limit your ability to sell through UK independent bookstores and libraries.
• UK book retailers often check ISBN registries and may reject titles without UK-assigned ISBNs.
• Buying a block is more cost-effective if you plan multiple titles or editions.

You can purchase ISBNs from nielsenisbnstore.com. When you register, you’ll receive your ISBNs and the necessary metadata fields for UK distribution.

Print Paper and Colour Options

KDP offers various paper types—cream or white for paperbacks, and colour options for print interiors. UK readers typically expect cream for fiction and white for non-fiction or art books. This preference is rooted in traditional UK publishing standards.

Choosing the right paper type affects your file preparation:

• Cream paper slightly alters colour perception, so calibrate your PDFs accordingly.
• White paper is best for colour illustrations, charts, or photography-heavy books.

VAT and Pricing

Print books are zero-rated for VAT in the UK, meaning you don’t add VAT to your retail price. However, ebooks sold through Amazon are subject to VAT at 20%. This affects your royalty calculations and how you price your book on Amazon UK.

Example: If you price your ebook at £2.99, Amazon deducts 20% VAT before calculating royalties. Keep this in mind when setting prices to maintain profitability.

Market Size and Competition

The UK publishing industry was worth £7.1 billion in 2023, with self-publishing growing 68% over five years. Amazon KDP dominates this sector, but UK readers and retailers have higher expectations than in some other markets.

Your book competes not only on price but presentation. Proper formatting, professional covers, and UK-specific metadata improve discoverability and sales potential.

Regional Formatting Preferences

• UK English spelling conventions (e.g., “colour” vs “color”) should be consistent throughout your manuscript and metadata.
• Date formats, measurements, and other locale-specific details should reflect UK standards to avoid alienating readers.

Common Mistakes and How to Avoid Them

From my experience running publishing.co.uk and working with thousands of authors, the most frequent errors around KDP file formats are:

1. Submitting Word Files for Print

Many UK authors upload raw Word docs for print interiors, hoping KDP will convert them cleanly. It rarely works. The result? Cropped text, misaligned margins, or font substitution. Always submit properly formatted PDFs for print.

2. Ignoring Bleed and Gutter Settings

Failing to include appropriate bleed or gutter margins leads to text or images being cut off or lost in the spine. This is especially critical for thicker books.

3. Using Low-Resolution Images

Amazon requires at least 300 dpi for print images. Using anything less results in blurry or pixelated covers and interior illustrations.

4. Overcomplicating eBook Files

Authors sometimes try to force complex layouts into Kindle eBooks, which are designed for simple, reflowable text. This leads to rendering errors. Keep formatting simple and test on multiple Kindle devices.

5. Relying on Cheap Fiverr Formatters

I hired a formatter for £130 once who delivered a mess—missing chapters, broken TOCs, and inconsistent fonts. Fiverr gigs are often a false economy. The UK market is unique, and many freelancers lack the local knowledge or Amazon KDP expertise.

6. Not Ordering Print Proof Copies

Skipping print proofs to save money is false economy. I’ve seen countless UK authors publish books with formatting and colour issues that a proof copy would have caught. Investing £10 for a physical proof can save hundreds in returns and reputation damage.

Tools and Resources for UK Authors

Formatting Software

• Microsoft Word: Industry standard. Use styles and page layout settings carefully. Most UK authors start here.
• Calibre: Free open-source tool for ebook conversion, primarily used for EPUB and MOBI. Powerful but requires some learning curve.
• Adobe InDesign: Best for complex print layouts and professional cover design. Expensive but worth it for serious publishers.
• Kindle Previewer: Essential for checking ebook formatting across devices.
• Sigil: Open-source EPUB editor for advanced users who want fine control over EPUB files.
• Vellum: Mac-only, premium software that produces clean, professional ebooks and print files with minimal fuss. Not cheap but great for UK authors serious about quality.

Validation Tools

• W3C EPUB Validator: Checks EPUB files for compliance.
• Adobe Acrobat Pro: For PDF optimisation and ensuring print-ready files, including embedding fonts and checking colour profiles.

Professional Services

At publishing.co.uk, we automate the formatting process to deliver KDP-ready files tailored for the UK market. This saves hours and removes guesswork, especially if you’re not confident with technical details or want to avoid costly mistakes. Running one of the UK’s largest book review platforms, LoveReading.co.uk, and managing Amazon growth agency MrPrime.com, I’ve seen firsthand how critical proper formatting is for success.

UK Industry Bodies and ISBNs

• Nielsen ISBN Agency: The sole UK ISBN provider (nielsenisbnstore.com).
• Society of Authors: Offers resources and guidance for UK self-publishers.
• Book Industry Communication (BIC): UK trade body setting standards for book publishing, including metadata and barcodes.

Tool comparison matrix showing pros and cons for each formatting software

Cost Breakdown: What UK Authors Should Budget For

Publishing in the UK isn’t free, and understanding costs upfront can prevent nasty surprises.

Many UK authors try to DIY their formatting to save money, but poor formatting can cost sales and credibility. Investing wisely here is crucial.

Expert Tips from 25 Years in the Industry

1. Think Commercial, Not Just Technical

Your file format isn’t just about passing KDP’s upload requirements—it’s about how your product looks on Amazon and in readers’ hands. A clean, well-structured EPUB improves your Kindle ranking and reader satisfaction.

2. Test Early and Often

Start testing your formats early using Kindle Previewer and print proofs. Waiting until the last minute to upload often results in rushed corrections and delays.

3. Avoid Overly Complex Layouts for Kindle

Kindle devices don’t handle fancy layouts well. Use simple paragraph styles and avoid multi-column text or embedded fonts that aren’t widely supported.

4. UK Market Expectations Are Higher Than You Think

Readers and bookstores in the UK expect print books to meet traditional standards. Using a free Amazon ISBN might save money but can limit your book’s credibility and availability in UK retail.

5. Use Publishing.co.uk to Save Time and Headaches

Before publishing.co.uk existed, I personally suffered through hiring a so-called “expert” formatter for £130 who delivered a mess. I then tried Fiverr—that was worse. The automated tools were terrible. If you want to avoid the same pain, using a UK-focused, automated formatting service is worth every penny.

6. Budget for Proofs and Revisions

Don’t underestimate the importance of ordering print proofs and spending time reviewing them. You’ll catch issues no screen previewer can show.

7. Keep Metadata Consistent and UK-Friendly

Your book title, author name, and description should all use UK English spelling and conventions. Mismatched metadata can confuse retailers and reduce discoverability.

Checklist infographic for key KDP file format requirements

Real-World Case Studies and Examples

Case Study 1: Sarah’s Crime Thriller—Avoiding Print Formatting Pitfalls

Sarah, a UK author from Manchester, self-published her crime thriller using KDP. She initially uploaded a raw Word file as a print interior and chose an Amazon free ISBN. Sales stalled, and she received complaints about badly cropped text and poor spine alignment.

After investing £174 for a block of Nielsen ISBNs, hiring a professional formatter via publishing.co.uk (£50), and ordering print proofs, Sarah’s next edition was flawless. Her book gained traction in Waterstones and local indie bookstores, boosting sales by 35% within three months.

Case Study 2: James’s Non-Fiction Guide—eBook Formatting and VAT Confusion

James, based in Edinburgh, launched a business guide priced at £4.99 as an ebook. Unaware of VAT implications, he priced the book without considering the 20% VAT on ebooks, reducing his royalties unexpectedly.

After adjusting his price to £5.99 and reformatting his ebook with Calibre and Kindle Previewer to fix TOC issues, his royalties improved by 22%. He also purchased a UK ISBN to increase his book’s professional credibility.

Case Study 3: Emma’s Children’s Book—Importance of Colour Prints and ISBNs

Emma published a children’s picture book requiring full-colour print. She initially used Amazon’s free ISBN and white paper. UK readers and retailers expected cream paper for authenticity, and the free ISBN listed Amazon as publisher.

By switching to a Nielsen ISBN (£93), choosing cream paper, and commissioning a professional cover with barcode, Emma’s book was accepted by several UK schools and libraries, increasing bulk sales.

Comparison with Alternative Publishing Approaches

Self-publishing on KDP is not the only route for UK authors. Here’s how it stacks up against alternatives:

For UK authors serious about retail presence beyond Amazon, owning your ISBN and preparing flawless KDP files is essential even if you use IngramSpark or hybrid routes.

Frequently Asked Questions

What is the most common mistake UK authors make with KDP file formats?

Submitting a Word document for print without converting it properly to a PDF with correct trim size, margins, and bleed is the biggest culprit. This causes formatting disasters and delays in publication.

How much do KDP file formats cost in the UK?

Costs vary. Nielsen ISBNs are £93 for a single or £174 for 10. Professional formatting services cost between £100 and £300+, though automated UK-specific services like publishing.co.uk start at £25. Print proofs cost £5–£15 per copy.

What tools do UK authors recommend for KDP file formats?

Microsoft Word for manuscript prep, Calibre for ebook conversion, Adobe InDesign for print layout, and Kindle Previewer for checking output are popular. For UK-specific formatting, professional or automated services ensure compliance and quality.

How long does formatting for KDP typically take?

If you DIY, expect several days to weeks depending on your skill and manuscript size. Professional services can turn around files in hours to a few days.

Can I handle KDP file formats myself, or should I hire a professional?

If you’re confident with Word styles, PDF exports, and EPUB conversion, you can do it yourself. But most UK authors find the process overwhelming. Hiring a UK-focused professional or using automated services saves time, reduces errors, and improves your book’s presentation.

What are the UK-specific requirements for KDP file formats?

UK authors must consider Nielsen ISBNs, VAT on ebooks, trim sizes preferred by UK printers (5” x 8”, A5), and paper type choices (cream vs white). Barcodes follow the EAN-13 standard in the UK. These factors impact everything from printing to retail acceptance.

Publishing on KDP is more than just uploading a file. With the right preparation, understanding of UK-specific factors, and utilising professional tools or services, you can ensure your book is polished, professional, and ready to succeed in the competitive UK market.

About the Author

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 and 15 successful exits, 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 largest book review platform), founder of the Amazon growth agency MrPrime.com, and a member of the Forbes Business Council.

This guide is designed to empower UK authors with the knowledge and tools to master KDP file formats confidently and cost-effectively, helping you avoid common pitfalls and maximise your book’s potential on Amazon and beyond.