Free tool
KDP spine width calculator
The spine width and full cover size for a KDP paperback — from your page count, trim size and paper, using KDP’s own formula.
The final count from your interior PDF, including blank pages. Change it and the spine changes.
Spine width
0.450"
200 pages × 0.002252" per page
Full cover, with bleed
12.700" × 9.250"
Back, spine and front, plus 0.125" bleed on every outside edge.
Text on the spine
Allowed
Keep it at least 0.0625" in from each spine edge.
Why the spine is the number that gets covers rejected
The front and back of a paperback cover are fixed by the trim size. The spine is the only part that moves — and it moves with every page you add or cut. A cover designed for 200 pages and uploaded with a 212-page interior is the wrong width, and KDP will send it back.
So design the cover last, after the interior is final. If the page count changes, come back here and the spine changes with it.
What to keep clear
- Bleed — 0.125" on the top, bottom and outside edges is cut off after printing. Extend background colour and images into it; keep text out of it. See bleed.
- Barcode — KDP prints one on the back cover, bottom right, about 2" × 1.2". Leave that area plain.
- Spine text — allowed above 79 pages, and kept 0.0625" in from each spine edge.
Setting up the canvas
KDP wants covers at 300 DPI. Switch the calculator to pixels and it gives you the exact canvas size for Figma, Canva, Photoshop or Affinity — the full wrap, bleed included. Export as a single PDF, not separate front and back images.
Questions people ask
How does KDP calculate spine width?
Page count multiplied by the thickness of one page: 0.002252" for white paper, 0.0025" for cream, 0.002347" for premium colour and 0.002252" for standard colour. A 200-page book on white paper has a 0.450" spine.
How big should my full paperback cover be?
Bleed + back cover + spine + front cover + bleed across, and bleed + trim height + bleed down, with 0.125" of bleed on each outside edge. For a 6" × 9" book with 200 white pages that is 12.700" × 9.250" — 3,810 × 2,775 pixels at 300 DPI.
Can I put text on the spine?
Only if the book has more than 79 pages. Below that the spine is too thin to print text on reliably, and KDP rejects covers that try. Keep spine text at least 0.0625" in from each side of the spine.
Why does another calculator give a different number?
Some add a fixed allowance to the spine that is not in KDP’s published formula. This one uses KDP’s formula and nothing else. Whichever you use, download the final template from KDP’s own cover calculator once your page count is final.
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