The spine and the cover
The spine width, the cover file dimensions, the interior page size and the printing cost — from the formulas Amazon publishes.
This application is served by KNPLIV and runs sandboxed: it cannot read your sign-in details, store anything on your device, or send in the background what you type into it. Everything is gone when you leave the page. Like everything published here, it was read over before going online.
A spine that is too narrow shifts all the cover artwork, and Amazon only says so after you upload. Its width cannot be guessed: it depends on the page count and the paper, through a formula Amazon publishes but never applies for you.
This tool applies that formula, then works out the exact dimensions of the full cover file — back, spine, front and bleed — with a diagram drawn to scale. It also gives the interior page size, which does not grow the way the cover does, and the printing cost per copy.
Every figure was taken from Amazon’s help pages on 6 September 2026, each one read and then reopened by a second researcher whose job was to contradict it. Where two of Amazon’s pages contradict each other — the colour coefficient, the threshold above which a spine may carry text — both versions are shown rather than settled. Whatever could not be confirmed is not displayed: better a blank than a figure that would have a book printed and refused.
Nothing is sent anywhere: everything is worked out in your browser.