KDP spine width calculator
KDP spine width = page count × paper thickness: 0.002252 in per page on white paper, 0.0025 in on cream, 0.00235 in on groundwood and 0.002347 in on premium color. In millimeters that is 0.0572 mm per page on white and 0.0635 mm on cream, so 200 pages on white paper make a 0.45 in (11.4 mm) spine. Hardcovers add 0.189 in. Spine text needs a book with more than 79 pages.
By kdpbook.io editorialUpdated ✓ Checked against KDP Help on
0.0025 in per page on this paper.
Every page counts, including blank and front-matter pages. KDP rounds odd counts up.
For a 200-page black & white paperback on cream paper, KDP’s spine is 0.5 in (12.7 mm).
- Pages used:
- 200
- Formula:
- 200 × 0.0025 in
- Spine margin:
- 0.0625 in each side
- Full cover:
- 12.75 × 9.25 in
Keep spine text 0.0625 in away from both folds: the fold can shift by up to 0.0625 in in production.
Cite this tool
kdpbook.io, “KDP spine width calculator”, https://kdpbook.io/kdp/spine-width-calculator (checked against KDP Help on ).
How KDP calculates spine width
A paperback spine is simply the stack of paper inside it. KDP publishes a thickness per page for each paper and multiplies it by your page count. Page counts are always even: KDP prints on both sides of each sheet, so an odd count is rounded up to the next even number before the spine is calculated.
| Ink & paper | Per page | 100 pages | 300 pages |
|---|---|---|---|
| Premium color · white paper | 0.002347 in · 0.0596 mm | 0.235 in | 0.704 in |
| Standard color · white paper | 0.002252 in · 0.0572 mm | 0.225 in | 0.676 in |
| Black & white · white paper | 0.002252 in · 0.0572 mm | 0.225 in | 0.676 in |
| Black & white · cream paper | 0.0025 in · 0.0635 mm | 0.25 in | 0.75 in |
| Black & white · groundwood paper | 0.00235 in · 0.0597 mm | 0.235 in | 0.705 in |
The same factors are used by KDP’s own cover calculator. Our numbers are checked against it; the only difference is that we always use the even page count KDP prints, while the public calculator uses the number exactly as typed.
KDP spine width by page count
Paperback spine widths for common page counts on white, cream and premium color paper, from the same formula as the calculator. A dash means the page count is above KDP’s limit for that paper on the standard trims, from 5 × 8 to 8 × 10 in. Spine text follows KDP’s rule: spine text only on books with more than 79 pages.
| Pages | White | Cream | Premium color | Spine text |
|---|---|---|---|---|
| 24 | 0.054 in | 0.06 in | 0.056 in | No |
| 50 | 0.113 in | 0.125 in | 0.117 in | No |
| 75 prints as 76 | 0.171 in | 0.19 in | 0.178 in | No |
| 100 | 0.225 in | 0.25 in | 0.235 in | Allowed |
| 150 | 0.338 in | 0.375 in | 0.352 in | Allowed |
| 200 | 0.45 in | 0.5 in | 0.469 in | Allowed |
| 250 | 0.563 in | 0.625 in | 0.587 in | Allowed |
| 300 | 0.676 in | 0.75 in | 0.704 in | Allowed |
| 400 | 0.901 in | 1 in | 0.939 in | Allowed |
| 500 | 1.126 in | 1.25 in | 1.173 in | Allowed |
| 600 | 1.351 in | 1.5 in | 1.408 in | Allowed |
| 700 | 1.576 in | 1.75 in | 1.643 in | Allowed |
| 800 | 1.802 in | – | 1.878 in | Allowed |
Hardcover spines
KDP hardcovers are case laminate: the cover is wrapped around rigid boards. The spine is the paper thickness plus 4.8 mm for the boards and the binding. Hardcovers need between 75 and 550 pages and are only offered on premium color · white paper, black & white · white paper, black & white · cream paper.
When can the spine carry text?
KDP only prints spine text on books with more than 79 pages, and asks for 0.0625 in of clear space between the text and each fold, because folds can move by up to 0.0625 in during binding. On a thin spine, those margins leave almost no room for type. kdpbook therefore only sets spine text when the safe area can hold 7 pt type, KDP’s minimum text size:
- Premium color · white paper: spine text from 96 pages
- Standard color · white paper: spine text from 100 pages
- Black & white · white paper: spine text from 100 pages
- Black & white · cream paper: spine text from 90 pages
- Black & white · groundwood paper: spine text from 96 pages
Mistakes that get covers rejected
- Making the cover before the interior is final. Add 20 pages and the spine grows by about 0.05 in on cream paper.
- Choosing a different paper in KDP than the one used for the cover. Switching from white to cream widens the spine by about 11%.
- Putting text on the spine of a book under 80 pages, or too close to the folds.
Next step: turn the spine width into a full cover with the cover size calculator, which also gives you a template to design on.
How to use it
- 01
Pick the binding
Paperback or hardcover. Hardcovers add the board thickness to the spine.
- 02
Pick ink and paper
The paper decides the thickness per page. Cream is thicker than white.
- 03
Enter the page count
Use the interior's real page count, including front matter and blank pages.
- 04
Use the width
Put the spine width in your cover layout, or let the cover size calculator build a template.
Questions
How wide is the spine of a 100-page KDP paperback?
0.225 in on white paper and 0.25 in on cream paper. KDP multiplies the page count by a per-page factor for the paper you choose.
Does KDP add 0.06 in to the spine width?
No. KDP's paperback spine is page count × 0.002252 in on white paper (200 pages = 0.45 in), the factor KDP's own cover calculator uses. The 0.06 in some calculators add isn't part of KDP's formula; KDP's 0.0625 in is the clear space between spine text and each fold, not extra width.
Why does the paper type change the spine width?
Each paper has its own thickness. Cream paper is the thickest (0.0025 in per page), then groundwood (0.00235), premium color (0.002347) and white or standard color (0.002252).
How many pages do I need for text on the spine?
KDP prints spine text only on books with more than 79 pages and asks for 0.0625 in of space between the text and each fold. In practice a very thin spine can't hold readable type: kdpbook enables spine text once the spine is wide enough for 7 pt type, from 90 pages on cream paper and 100 on white.
Is the spine included in the cover width?
Yes. A paperback cover is one flat image: bleed, back cover, spine, front cover, bleed. The spine sits between the two covers, so every page you add makes the whole cover wider.
What happens if my page count changes after I make the cover?
The spine changes too, and KDP rejects covers whose spine doesn't match the interior. Recalculate the cover every time the interior's page count changes. kdpbook sizes the cover from the final interior automatically.
How is a hardcover spine calculated?
KDP adds 4.8 mm (0.189 in) for the boards to the paper thickness, so a hardcover spine is always wider than the same book in paperback.