KDP spine width calculator
The same formulas our build engine runs on every book, free to use on their own. Pick a binding and paper stock, enter your final page count, and get the exact spine width for your cover file.
Enter your book's specs
Hardcover spine width uses the commonly accepted board-allowance model (no official KDP formula is published for hardcover) — verify against KDP's own Cover Calculator before finalizing a hardcover cover file. Every Typesheep build does this automatically and generates the cover template for you.
Spine width by page count
Common page counts, computed with the formulas above. For any other page count, use the calculator.
Paperback
| Pages | White (0.002252in/pp) | Cream (0.0025in/pp) | Premium color (0.002347in/pp) |
|---|---|---|---|
| 24 (minimum) | 0.054in / 1.4mm | 0.060in / 1.5mm | 0.056in / 1.4mm |
| 100 | 0.225in / 5.7mm | 0.250in / 6.4mm | 0.235in / 6.0mm |
| 150 | 0.338in / 8.6mm | 0.375in / 9.5mm | 0.352in / 8.9mm |
| 200 | 0.450in / 11.4mm | 0.500in / 12.7mm | 0.469in / 11.9mm |
| 300 | 0.676in / 17.2mm | 0.750in / 19.1mm | 0.704in / 17.9mm |
| 400 | 0.901in / 22.9mm | 1.000in / 25.4mm | 0.939in / 23.8mm |
| 500 | 1.126in / 28.6mm | 1.250in / 31.8mm | 1.174in / 29.8mm |
| 700 | 1.576in / 40.0mm | 1.750in / 44.5mm | 1.643in / 41.7mm |
| 776 (cream max) | 1.748in / 44.4mm | 1.940in / 49.3mm | 1.822in / 46.3mm |
| 828 (white/premium max) | 1.865in / 47.4mm | — | 1.943in / 49.4mm |
Hardcover (spine-per-page + 0.25in board allowance)
| Pages | White (0.002252in/pp + 0.25in) | Cream (0.0025in/pp + 0.25in) |
|---|---|---|
| 75 (minimum) | 0.419in / 10.6mm | 0.438in / 11.1mm |
| 150 | 0.588in / 14.9mm | 0.625in / 15.9mm |
| 250 | 0.813in / 20.6mm | 0.875in / 22.2mm |
| 350 | 1.038in / 26.4mm | 1.125in / 28.6mm |
| 450 | 1.263in / 32.1mm | 1.375in / 34.9mm |
| 550 (maximum) | 1.489in / 37.8mm | 1.625in / 41.3mm |
Where these numbers come from
Paperback: spine width in inches equals page count multiplied by a fixed per-page thickness that depends on paper stock: 0.002252in for white or premium color paper, 0.0025in for cream. Cream paper is thicker per sheet, which is why the same page count produces a wider spine.
Hardcover: KDP publishes no official spine formula for hardcover the way it does for paperback. The model used here, and by most cover designers, applies the same per-page thickness as paperback and adds a fixed 0.25in board allowance to account for the two binder boards and the crash (the fabric strip reinforcing the spine fold). Treat this as a close estimate, not a guarantee, and check the exact figure against KDP's own Cover Calculator for your specific trim before sending a hardcover cover to print.
Books under 80 pages can't legally carry spine text at all on KDP, because the spine is too narrow to hold readable type. The calculator above doesn't block that page count, but a build through Typesheep will flag it and adjust your cover template automatically.
Common questions about KDP spine width
What is the formula for KDP paperback spine width?
Spine width in inches equals page count times the per-page thickness for your paper stock: 0.002252in for white or premium color, 0.0025in for cream. A 300-page book on white paper is 300 × 0.002252 = 0.6756in.
What is the formula for KDP hardcover spine width?
KDP publishes no official hardcover spine formula. The commonly used model is the same per-page thickness as paperback (white 0.002252in, cream 0.0025in) plus a 0.25in board allowance. A 300-page hardcover on white paper works out to (300 × 0.002252) + 0.25 = 0.9256in. Confirm against KDP's own Cover Calculator before finalizing a hardcover cover.
How many pages can a KDP paperback or hardcover have?
Paperback: 24 to 828 pages on white or premium color paper, 24 to 776 on cream. Hardcover: 75 to 550 pages on white or cream.
Why does my spine width matter before I design a cover?
It sets the total width of your cover file: back cover plus spine plus front cover, plus bleed. Get it wrong and spine text is misaligned, crushed, or missing on a book too thin to carry it (under 80 pages, spine text isn't allowed). Typesheep computes this from your real final page count and builds the cover template with the spine already placed correctly.