KDP Cover Calculator

Spine width is your page count times a per-page paper-thickness constant that depends on your paper color and interior ink type (white, cream, groundwood, standard color, or premium color). Hardcover adds a fixed board-thickness offset on top of that.

Full-wrap width in inches × 300, and height in inches × 300, because KDP prints at 300 DPI. A 6 × 9in, 200-page paperback on white paper has a 0.450in spine and a 12.700 × 9.250in cover with bleed, which is 3,810 × 2,775 px. The page count and paper change the spine, so the pixel width changes with them — the calculator above shows the pixel size for your exact book.

The numbers are. KDP publishes the formula — a per-page paper thickness for each paper and ink, plus 0.125in of bleed — and this calculator uses those published constants, each dated on this page against the KDP help page it came from. KDP also offers its own cover template download; use either. If the two ever disagree, trust KDP's. What this page adds is the pixel size at 300 DPI, groundwood paper, a hardcover estimate and ready-made pages for the commonest sizes.

Yes. Groundwood is KDP's cheaper black-ink paper for paperbacks, and its pages are thicker than white and thinner than cream: KDP's spine formula for it is page count × 0.00235in. Pick Groundwood under Paper color and the spine and full-cover width update. If you switch an existing book to groundwood, resize its cover, because the spine width changes. KDP prints no groundwood hardcovers, and groundwood books stop at 812 pages on most trims (fewer on the largest ones). The Cover Template Generator and Cover Designer don't offer groundwood yet.

One is the trim-based size (no bleed) and one adds KDP's standard 0.125in bleed on every outer edge except the spine folds. Submit the with-bleed size as your actual cover file — KDP trims the bleed off after printing.

The paperback formula uses KDP's own published per-page thickness constants. The hardcover formula is not KDP-published: it is our own, built from real KDP hardcover dimensions and checked against them across every trim size and paper type we tested. Treat it as an estimate and verify against KDP's official template download before final print submission.

KDP's own rule is 79: it only prints spine text on books with more than 79 pages. Legibility is a separate question, and it is ours, not KDP's. KDP requires 0.0625in of clear space on each side of spine text, so an 80-page black-and-white interior leaves about 0.055in of type height once that clearance is taken — roughly 4pt, which is smaller than most footnotes. At 150 pages you have about 0.213in, or roughly 15pt. We suggest treating about 150 pages as the practical floor for spine text you actually want someone to read.

The dashed inner line is KDP's published text-safety margin (0.125in inset from the trim edge on the front and back cover) — keep any text or important imagery inside it so it isn't cut during trimming.

The placeholder box on the back cover is KDP's standard barcode area (2in × 1.2in, bottom-right, inset from the safe area) — KDP can generate your barcode automatically at upload, or you can place your own ISBN barcode there.