KDP Spine Width Calculator
Calculate paperback spine width from page count and paper type.
What is the KDP Spine Width Calculator?
Your paperback's cover file needs an exact spine width to line up the front cover, spine text and back cover correctly. Amazon KDP calculates spine width from your page count and interior paper type using a fixed per-page thickness.
The formula
Spine width (inches) = page count × paper thickness factor: white paper ≈ 0.002252"/page, cream paper ≈ 0.0025"/page, standard color ≈ 0.0032"/page, premium color ≈ 0.002252"/page.
A note on accuracy
These per-page constants come from Amazon KDP's published cover template guidance, cross-checked against multiple current publishing resources. The premium color constant in particular is cited slightly differently across sources, so before submitting your final cover file, always confirm the exact spine width using Amazon's own official KDP Cover Calculator — it's the authoritative source and will catch any recent formula changes this tool might not yet reflect.
How to use it
- Enter your final interior page count (after formatting, not your manuscript word count).
- Select the paper type you've chosen for your interior.
- Use the resulting spine width to build your cover template, or as a sanity check against a template you've already downloaded from KDP.