KDP help
KDP Cover Size & Spine Width Guide
A KDP paperback cover is one full-wrap file: back cover, spine and front cover in a single PDF, sized to the exact fraction of an inch. Get the spine width wrong and KDP rejects the cover. Here's how the numbers work — and the quickest way to get them right.
The full-wrap cover formula
Your cover PDF page size is:
- Width = back cover (trim width) + spine width + front cover (trim width) + 0.25″ bleed
- Height = trim height + 0.25″ bleed
For an 8.5″ × 8.5″ book with a 0.225″ spine, that's a cover of 17.475″ × 8.75″.
Spine width by paper type
Spine width = page count × paper thickness:
| Paper type | Thickness per page |
|---|---|
| White (black & white books) | 0.002252″ |
| Cream (black & white books) | 0.0025″ |
| Colour printing | 0.002347″ |
Worked examples
| Book | Spine width | Notes |
|---|---|---|
| 24 pages, white | 0.054″ | Too thin for spine text (KDP minimum ~79 pages) |
| 100 pages, white | 0.225″ | Spine text allowed |
| 200 pages, cream | 0.5″ | Spine text allowed |
| 300 pages, colour | 0.704″ | Spine text allowed |
KDP only prints text on the spine when the book is thick enough (around 79 pages or more).
The barcode area
KDP prints the barcode in a 2″ × 1.2″ area at the bottom right of the back cover. Keep important text and artwork out of that area, and keep all text at least 0.25″ from the trim edges and spine folds.
Skip the maths
The KDP Ready Cover Converter works all of this out for you:
- Enter your trim size, page count and paper type.
- Upload your front and back artwork (or generate a cover).
- Download a full-wrap cover PDF at the exact size KDP expects — spine calculated, barcode area kept clear, 300 DPI.
Questions
How do I work out my KDP spine width?
Multiply your page count by the paper thickness. For white paper use 0.002252 inches per page, for cream paper 0.0025 inches, and for colour printing 0.002347 inches. A 100-page book on white paper has a 0.2252 inch spine.
How big should a KDP full-wrap cover be?
The total width is back cover + spine + front cover, plus 0.125 inches of bleed on every outside edge. The height is your trim height plus 0.25 inches of bleed (top and bottom).
Where does the barcode go on a KDP cover?
KDP places the barcode in the bottom right of the back cover, in a 2 x 1.2 inch area. Keep that area clear of important text or artwork, or KDP will reject the cover.
Can KDP Ready build my cover for me?
Yes. Enter your trim size, page count and paper type and the Cover Converter calculates the spine width and builds a full-wrap cover at the exact size KDP expects, with the barcode area kept clear.