Publishing Intelligence.
Professional-grade instruments for independent publishing. From mathematical royalty forecasting to exact physical spine modeling — synchronized with 2026 KDP standards.
Royalty Estimator
Instantly estimate your net earnings across US, UK, India, and European marketplaces. Includes marketplace fees and variable printing costs.
Launch ToolSpine Expert
Calculate exact spine width for white and cream stocks. Uses official KDP Paper Point Index constants for manufacturing accuracy.
Launch ToolNew to self-publishing?
Every term explained — PPI, bleed, trim size, royalties, and more.
Standard Trim Sizes
Research & Notes.
In-depth articles on the math and logic behind our tools — written for people who want to understand the calculations, not just run them.
How to Calculate KDP Spine Width Without Getting Your Cover Rejected
A spine width miscalculation is the single most common reason KDP rejects a cover file. Here is the exact formula, the constants, and the edge cases that trip up most authors.
KDP vs IngramSpark: Which Pays Better Royalties in 2026?
Both KDP and IngramSpark promise broad distribution, but their royalty structures are fundamentally different. Here is an honest comparison of which platform pays more and when.
Why Your Book Spine Goes Blank: The 80-Page Rule Explained
KDP will not print text on spines below a page count threshold. Here is the physics behind why, and what you can do about it if your manuscript is short.