"Cover dimensions do not match": what KDP measured, and how to fix it

The symptom. KDP rejects the cover upload, or the print previewer shows your cover shifted, cropped, or with the spine text in the wrong place. KDP is not judging your design — it measured your file's page size and compared it with the one expected size for your book. They differ.

The one equation behind every paperback cover

A paperback cover is a single wraparound file, and its size is fully determined by three inputs:

full width = 0.125 (bleed) + trim width (back) + spine + trim width (front) + 0.125 (bleed)
full height = trim height + 0.25 (bleed top and bottom)
spine = page count × per-page thickness — 0.002252 in/page for white paper, 0.0025 in/page for cream.

Worked example. A 6 × 9 in paperback, 200 pages, white paper: spine = 200 × 0.002252 = 0.450 in. Full cover = 0.125 + 6 + 0.450 + 6 + 0.125 = 12.700 × 9.250 in (3810 × 2775 px at 300 dpi). If your file is anything else — even 12.50 × 9.25 — it does not match. Compute your own in the spine & cover calculator.

The five usual causes

1. The cover was built at trim size, with no bleed. A 12.00 × 9.00 in file for the example above. The fix is not stretching — rebuild at the full size from the equation (see the bleed guide for why the extra 0.125 in exists).

2. Page-count drift. The most common cause in real projects: the cover was designed when the manuscript had 200 pages, a final edit brought it to 188, and the cover was never regenerated. The spine is now 0.027 in too wide, the file no longer matches, and the printed spine text sits off-center. Freeze the page count first, then make the cover.

3. Wrong paper type in the maths. Cream is thicker per page than white. A spine computed for white (0.450 in at 200 pages) should be 0.500 in on cream — a 0.05 in error, more than enough to fail.

4. A front-cover-only file. Paperback upload requires the full wrap (back + spine + front in one PDF). A single front-cover image — the file you would use for an ebook — can never match a wraparound specification.

5. A template for the wrong format. Hardcover wraps are built larger than paperback wraps for the same book (the case extends past the pages). A paperback template used for a hardcover, or a template downloaded for a different trim size, fails by construction.

The fix, in order

1. Freeze the interior. Final page count, final trim, final paper type — no cover work until these stop moving.
2. Compute the expected size with the equation above or the calculator; write the number down.
3. Rebuild or resize the cover to exactly that size, keeping art extended to the bleed edges and spine text inside the spine's safe area (see the spine guide).
4. Export a PDF at exactly that page size, fonts embedded.
5. Verify the file, not your memory of it: run it through the free pre-flight check — it reads the PDF's real page box and compares it against the specification, which is the same measurement KDP makes.

Rules summarized from KDP's published cover specifications, last checked 2026-11-09. KDP's own template generator (in your account) is the final authority for your exact book.