Guides and calculators.
Short, checked answers to the questions that come up between a finished manuscript and a launch post.
KDP spine width: how to work it out
The formula KDP uses for white, cream and colour paper, worked examples, the 79 page rule for spine text, and what the numbers look like on a real book.
Spine width calculator
Your page count and paper in, the spine width out, in inches and millimetres, with the full cover size for a KDP paperback.