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Calculate spine width, KDP print cost, royalties, illustration count & publishing timeline — all in one place. Trusted by self-publishing authors worldwide.
Planning a children's book is more than writing a story. Before you even send a word count to an illustrator, you need to know exactly how many pages your book will have, how wide the spine will be, how much it will cost to print on Amazon KDP, and how much royalty you'll earn per sale. The Kidillus Book Planner Pro calculates all of this instantly — for free.
Whether you're publishing a 24-page board book for toddlers, a 32-page full-color picture book for ages 3–7, or a longer chapter book, this tool handles every scenario. It supports Amazon KDP, IngramSpark, and five different marketplaces with live currency conversion.
The spine width is one of the most critical measurements in self-publishing. It is calculated from your total page count multiplied by the paper thickness — 0.002252 inches per page for standard color paper, 0.0025 inches for premium. If your cover design file uses the wrong spine width, Amazon will reject it outright. Our calculator gives you the exact figure including bleed allowance.
Amazon KDP pays 60% of your list price for standard distribution, minus the printing cost. For example, a $12.99 book with a $3.65 printing cost earns you $4.14 per sale. If you enable Extended Distribution, the royalty rate drops to 40%. Our planner shows you the full formula so you can set a price that's profitable before you publish.
The most popular trim size is 8.5″ × 8.5″ for square picture books — it looks professional and is widely accepted. For portrait-style books, 8″ × 10″ is the standard. Both are supported by KDP for paperback and hardcover.
The formula is: (List Price × 60%) − Printing Cost = Your Royalty. For instance, a $12.99 book with $3.65 printing cost yields ($12.99 × 0.60) − $3.65 = $4.14 per sale. Our tool shows this breakdown automatically.
A standard 32-page picture book (ages 3–7) typically needs 14–16 double-page spreads or 24–28 single-page illustrations, depending on your layout style. Our tool calculates this based on your word count, age group, and illustration style selection.
For Amazon KDP US, a 32-page standard color paperback costs approximately $3.65 to print. A premium color 32-page book costs around $3.87. Hardcover adds a base cost of $6.50 plus per-page charges. These figures are updated for 2026 and built into our calculator.
Yes! Kidillus provides end-to-end children's book services — custom illustrations, cover design, KDP-formatted interior layout, and ISBN barcode generation. After generating your plan, click Get Quote to start your project.
Yes. The spine width, page count, and cover dimension calculations are identical for IngramSpark. The royalty calculation uses IngramSpark's 55% rate when you select that distribution option.
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