KDP Cover Size & Spine Calculator
Exact full-wrap cover dimensions and spine width for paperback and hardcover — with and without bleed, DPI-correct pixel sizes, and a downloadable SVG cover guide.
Your cover dimensions
| Measurement | Inches | Centimeters | Pixels @300dpi | Points |
|---|---|---|---|---|
| Full cover width (with bleed) | 12.700 | 32.26 | 3810 | 914.4 |
| Full cover height (with bleed) | 9.250 | 23.50 | 2775 | 666.0 |
| Spine width | 0.450 | 1.14 | 135 | 32.4 |
Cover bleed is a flat 0.125in on every non-spine edge, per KDP's published spec (verified 22 July 2026). KDP prints spine text only on books with more than 79 pages (verified 31 July 2026); allow around 150 for type that stays comfortably legible after its required 0.0625in of clearance on each side.
Cover guide
How the formula works
Spine width is your page count times a per-page thickness constant, plus a fixed board offset for hardcover:
spine width = page count × per-page thickness [+ board offset]
Full-wrap cover width is two front covers plus the spine — with KDP's standard 0.125in bleed added on every edge except the spine folds:
cover width = (2 × trim width) + spine width [+ 2 × bleed]
Paperback constants come directly from KDP's public spine-width guidance. Hardcover constants are not KDP-published — they are fitted to a large reference dataset of real KDP hardcovers; see the FAQ below for the accuracy caveat.
The paperback per-page thickness constants were last checked against KDP's own cover guidance on 31 July 2026. Every other constant the result panel above uses — bleed, the spine-text minimum, and the hardcover fit — carries its own date there, since they were checked against different KDP pages on different days.
Turn these numbers into a template
The KDP Cover Template Generator takes the same trim size, page count and paper and gives you a print-ready PDF with the trim, bleed, spine, safe-zone and barcode guides drawn on it — plus a transparent 300 DPI PNG you can put on a layer above your artwork. It is free and needs no account, same as this page.
What a correct cover looks like being built
These dimensions are the input, not the finished job. The Cover Designer in Book Studio takes your trim size and page count and keeps the spine, bleed, safe margins and barcode zone correct while you design — then runs KDP’s preflight checks before it lets you export.
Common sizes, already worked out
Every combination below is a page of its own with the spine width, full-wrap dimensions and printing cost already computed — useful if you want the number without touching the calculator, or want to compare two page counts side by side.
Frequently asked questions
How is spine width calculated?
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, standard color, or premium color). Hardcover adds a fixed board-thickness offset on top of that.
Why does the calculator show two full-cover sizes?
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.
How accurate are the hardcover numbers?
The paperback formula uses KDP's own published per-page thickness constants. The hardcover formula is not KDP-published: it was fitted to a large reference dataset of real KDP hardcover dimensions and matched to within 0.001in 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.
How many pages do I need for spine text?
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.
What's the safe area on the cover guide?
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.
Where does the barcode go?
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.
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