🛠️ Author Toolkit

Free Professional Tools for
Self-Publishing Authors

From KDP spine calculations to ISBN barcode generation, EPUB creation, and Amazon description formatting — every tool you need to publish professionally, completely free.

No Sign-up Required
🔓 100% Free Forever
📦 KDP & IngramSpark Ready
🌍 Used by 1,000+ Authors
💡 Ad-Supported to Stay Free
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Plan Your Book
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Calculate Dimensions
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Format Content
4
Generate EPUB
5
Add ISBN Barcode
6
Publish on KDP

💡 Keeping It Free: These tools are supported by advertisements — covering maintenance costs while remaining 100% free for every author, forever.

Everything You Need — No Cost, No Catch

Seven professional-grade tools built for children's book authors. Browser-based, instant, and designed to match the standards Amazon KDP and IngramSpark require.

7
Free Tools Available
1,000+
Authors Using Tools
0
Sign-ups Required
100%
Browser-Based
Free
Forever

Why Authors Use Kidillus Tools

Technical publishing errors cost authors weeks of delays and KDP rejections. These tools eliminate the most common problems before they happen.

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Eliminate KDP Upload Rejections
Incorrect spine widths, wrong bleed, missing image resolution — our calculator tools surface these problems before you brief your designer, not after you've paid for artwork.
Browser-Based — No Downloads
Every tool runs in your browser. No software to install, no account to create, no compatibility issues. Works on Mac, Windows, iPad, or any modern device.
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Built to KDP & IngramSpark Specs
Every calculation and output is built against current Amazon KDP and IngramSpark technical requirements. We update the tools whenever the platforms change their specs.
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Save Hundreds in Freelancer Costs
A spine width calculation from a freelance designer can cost £50–£100. Our cover calculator delivers the same output in 30 seconds for free — with the same professional accuracy.
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Your Data Stays Private
Nothing is stored, nothing is sent to a server. ISBN numbers, book details, and manuscript content you enter into our tools are processed locally and never leave your browser.
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Used by Authors on Four Continents
Authors in the US, UK, Canada, Australia, India, and beyond use these tools daily. They're built for the global self-publishing market, not one region's specs.

Kidillus Tools vs Doing It Manually

Here's what authors experience trying to calculate specifications, create barcodes, and format descriptions manually — versus using the right tools from the start.

Task Without Tools With Kidillus Tools
Spine width calculation⚠ Error-prone manual formula✓ Instant & accurate
KDP cover dimensions✗ Trial and error uploads✓ Exact specs in seconds
ISBN barcode generation⚠ Paid third-party services✓ Free, 300 DPI instant
Amazon description HTML✗ Manual HTML coding✓ Visual editor, one click
EPUB file creation✗ Complex software required✓ Upload & convert
Page layout planning⚠ Pen and paper or spreadsheets✓ Visual drag-and-drop
Project cost estimation✗ Guesswork✓ Itemised cost planner
Illustrator brief creation⚠ Incomplete emails✓ Professional PDF brief
Time to complete all of the above✗ Days✓ Under 30 minutes

Frequently Asked Questions

Are these tools really free — no hidden costs?
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Yes, completely free. Every tool on this page requires no account, no payment, and no sign-up. The tools are supported by advertising, which covers our maintenance and hosting costs. The only exception is the EPUB Generator, which is free for a limited time during its launch period.
Are the KDP specifications in the Cover Calculator up to date?
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Yes. We monitor Amazon KDP and IngramSpark specification changes and update the calculator accordingly. The spine width formula, bleed requirements (3mm), and margin specifications are checked regularly. If Amazon changes their requirements, we update our tools within 48 hours.
Is my ISBN or book content saved when I use these tools?
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No data is stored or transmitted to our servers. All calculations and formatting happen locally in your browser. ISBNs, manuscript content, and any other information you enter into these tools are never logged, stored, or shared. Your data is entirely private.
Do the tools work for IngramSpark as well as Amazon KDP?
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Yes. The Cover Calculator and EPUB Generator both support IngramSpark specifications alongside KDP. Where the two platforms have different requirements (which is common for spine calculations and bleed), the tools clearly distinguish between them and output the correct values for each platform.
What is the difference between these free tools and your paid services?
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The free tools give you the calculations, templates, and technical outputs — but you still do the creative and design work yourself. Our paid services mean a professional illustrator, designer, and formatter do the actual work for you: creating the illustrations, building the cover, formatting the interior, and handling the entire upload process. The tools are for confident DIY authors; the services are for authors who want a professional, guaranteed result.
Does the EPUB Generator support fixed-layout picture books?
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Yes — and this is one of its most important features. Fixed-layout EPUBs preserve exact page positions, which is essential for children's picture books where illustrations and text must stay in precise positions. Standard reflowable EPUBs are not suitable for picture books. Our generator handles both formats: reflowable for text-led books and fixed-layout for illustrated picture books.

Need a Professional to Handle It For You?

The tools handle the calculations — our studio handles everything else. Custom illustration, cover design, KDP formatting, and full publishing support, all from one team.

Free Self-Publishing Tools for Children's Book Authors

Kidillus provides a complete suite of free, browser-based self-publishing tools for independent authors. Whether you are calculating your KDP cover dimensions for the first time or generating a professional ISBN barcode for your tenth title, these tools eliminate the most common technical errors that delay children's book publications.

Our tools cover every stage of the technical publishing workflow: planning your book layout with the Visual Paginator, calculating exact spine and cover dimensions with the Cover Calculator, creating your EPUB file with the Generator, formatting your Amazon description with the HTML Formatter, generating your ISBN barcode at 300 DPI, writing a professional illustrator brief, and building your full publishing timeline and cost estimate with the Book Planner.

All tools are built to current Amazon KDP and IngramSpark specifications and updated whenever the platforms change their requirements. No account is required, no data is stored, and every tool is completely free. For authors who want a professional team to handle illustration, design, and formatting, visit our full publishing services or Learning Hub for free guides on children's book publishing.

What Users Say about All Kidillus Tools

Real feedback from creators & authors.

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