How this calculator works
Paperback calculations use the current public KDP spine factors for white, cream, groundwood, premium color, and standard color interiors. Exact hardcover width is intentionally deferred to Amazon’s official template generator because no universal hardcover spine formula is published.
paperback width = bleed + back + spine + front + bleed
Frequently asked questions
Why is KDP bleed 0.125 inch instead of 3mm?
KDP specifies 0.125 inch, approximately 3.2mm, on the outside cover edges. It must not be replaced with a generic 3mm value.
When can a paperback include spine text?
KDP requires at least 79 pages and describes spine-text eligibility as more than 79 pages, so this tool marks 80 or more as eligible.
Why does hardcover open the official calculator?
Hardcover files include wrap, hinges, boards, and an Amazon-generated spine. A guessed full width could cause rejection, so the exact template should come from Amazon.