How wide is my book’s spine?
The spine width of a paperback depends on two things: the number of pages and the paper. Multiply them and you have it. This KDP spine width calculator uses Amazon KDP’s paper thickness values and shows the result in inches, millimetres and pixels, together with what you can put on the spine.
KDP paper thickness
| Paper | Per page | 300 pages |
|---|---|---|
| Black & white, white paper | 0.002252 in | 0.676 in |
| Black & white, cream paper | 0.0025 in | 0.75 in |
| Standard colour | 0.002252 in | 0.676 in |
| Premium colour | 0.002347 in | 0.704 in |
Spine text rules
- KDP allows spine text only on books with 79 pages or more.
- Leave at least 0.0625 in (1.6 mm) between the text and each spine edge, because the fold can shift slightly.
- The calculator shows the largest font size that fits for your spine.
- In the US and UK, spine text usually reads top to bottom.
Why it matters
If your cover file’s spine is wrong, KDP rejects it or the spine text wraps onto the front or back. Calculate the spine after your interior is final — even 10 extra pages change the width. Then make the full cover template with the book cover size calculator.
Don’t know the page count yet? Estimate it from your word count with the page count estimator.
How spine width is calculated
Spine width = page count × paper thickness per page. On Amazon KDP paperbacks:
| Interior | Inches per page | 300 pages |
|---|---|---|
| Black & white, white paper | 0.002252 | 0.676 in |
| Black & white, cream paper | 0.0025 | 0.75 in |
| Standard colour | 0.002252 | 0.676 in |
| Premium colour | 0.002347 | 0.704 in |
Cream paper is thicker, so the same book has a wider spine on cream than on white.
Spine text: only for thicker books
KDP allows text on the spine only when the book has more than 79 pages, and recommends keeping text well inside the spine edges because the fold can move slightly during printing. For thin books, leave the spine plain or use a solid colour.
Example
A 240-page novel on cream paper has a spine of 240 × 0.0025 = 0.6 in. The full cover width for a 6 × 9 in book is 0.125 + 6 + 0.6 + 6 + 0.125 = 12.85 in, and the height is 9.25 in. Get the complete cover layout with the cover size calculator.
Tips
- Calculate the spine after the interior is final — every extra page changes it.
- Choose white or cream before ordering the cover design.
- Use a spine colour that also works if the fold shifts a little onto the front or back.