Cover size checker
Enter the interior's details, then drop in the full cover PDF. If the size is wrong, the checker names the cause: the wrong paper, an outdated page count, or a front cover with no spine or back.
Why covers are so often the wrong size
A paperback cover is one sheet whose width depends on the spine. The spine is the page count multiplied by the thickness of the paper chosen at upload.
So switching from white to cream paper makes the cover wrong, and so does adding a chapter. KDP's rejection then names the dimensions, not the cause.
The four mistakes, and how they are told apart
A number that does not match is not a diagnosis. The common mistakes are tested in turn, stopping at the first that explains the difference exactly:
- The wrong paper. The paper is chosen at upload, often after the cover was made.
- An out-of-date page count. The interior changed after the cover was made, for example a spine for about 300 pages on a 328-page book.
- A front cover with no spine or back. Often the designer was not told that the file must include the back and the spine.
- A different trim size, with a spine that fits it. This usually means the trim selected at upload is wrong, not the artwork.
If none of the four fits, the measurement is reported as it is.
The two rules about spine text
KDP allows no spine text under 79 pages, because the spine is too thin. On a thicker book the folds can shift by up to a sixteenth of an inch in binding. Text closer to a fold than that can end up on the front or back.
Position is checked, not wording. Any line of type inside the spine band is measured against both folds, and the smaller distance is reported.
No cover yet? The spine and cover size calculator gives the measurements to draw to. The print PDF checker checks the interior.