KDP Editor › KDP spine width calculator and cover size formula
KDP spine width calculator and cover size formula
Updated 2026-10-22
A KDP paperback cover is one PDF that wraps around the book: back cover, spine and front cover side by side, plus 0.125 in bleed on every outside edge. The only number that changes with your book is the spine, and it depends on the page count and the paper.
Spine width per page
| Ink and paper | Spine per page |
|---|---|
| Black & white, white paper | 0.002252 in (0.0572 mm) |
| Black & white, cream paper | 0.0025 in (0.0635 mm) |
| Standard color, white paper | 0.002252 in (0.0572 mm) |
| Premium color, white paper | 0.002347 in (0.0596 mm) |
Spine width = page count × spine per page. Example: 300 pages on cream paper = 300 × 0.0025 = 0.75 in.
Full cover size formula
Width = 0.125 in bleed + back cover width + spine width + front cover width + 0.125 in bleed.
Height = 0.125 in bleed + trim height + 0.125 in bleed.
Keep text and important art at least 0.125 in inside the trim lines, keep spine text 0.0625 in away from each fold, and leave the 2 × 1.2 in barcode area in the bottom-right corner of the back cover (0.25 in from the bottom trim and from the spine) free – KDP prints the ISBN barcode there.
Worked examples (checked against the KDP Cover Calculator)
| Trim | Pages | Ink / paper | Spine | Full cover (W × H) | PDF points |
|---|---|---|---|---|---|
| 8.5 × 8.5 in | 30 | B&W white | 0.068 in | 17.318 × 8.75 in | 1246.864 × 630 pt |
| 8.5 × 8.5 in | 30 | Premium color | 0.07 in | 17.32 × 8.75 in | 1247.07 × 630 pt |
| 8.5 × 11 in | 24 | B&W white | 0.054 in | 17.304 × 11.25 in | 1245.891 × 810 pt |
| 6 × 9 in | 300 | B&W cream | 0.75 in | 13 × 9.25 in | 936 × 666 pt |
| 6 × 9 in | 120 | B&W white | 0.27 in | 12.52 × 9.25 in | 901.457 × 666 pt |
| 5.5 × 8.5 in | 200 | B&W cream | 0.5 in | 11.75 × 8.75 in | 846 × 630 pt |
| 8.5 × 11 in | 100 | Premium color | 0.235 in | 17.485 × 11.25 in | 1258.898 × 810 pt |
We checked the first four rows against the KDP Cover Calculator on 22 October 2026 and it returned exactly these values (for example 17.318 × 8.75 in for 8.5 × 8.5 in, 30 pages, white paper, and 13 × 9.25 in for 6 × 9 in, 300 pages, cream paper); the other rows use the same formula. The calculator rounds to three decimals.
Can I put text on the spine?
Only if the book has at least 79 pages. Thinner books get a spine under about 0.18 in – too narrow for readable text, and KDP rejects covers with spine text below that page count. (KDP’s own Cover Creator only offers spine text from 80 pages.) For a 30-page coloring book, leave the spine as plain color or a continuation of the back/front art.
Make the cover in your browser
The free KDP Cover Creator does this math for you: choose the trim, page count and paper, and it draws the bleed, trim, safe area, spine and barcode guides, lets you place your front art, back text and spine text, warns about anything KDP would reject and exports a single print-ready PDF at the exact size. Your images never leave your computer.
Open the KDP Cover Creator – free
Sources: KDP Help – Create a Paperback Cover, KDP Help – Barcodes, KDP Cover Calculator (read 22 Oct 2026). Always confirm with KDP’s calculator and previewer before publishing. KDP Editor is not affiliated with Amazon.