Find your KDP paperback spine width in inches and millimeters from page count and paper type. Free, no sign-up.
How spine width is calculated
Spine width = page count × paper thickness. KDP uses 0.002252 in per page for black & white on white paper, 0.0025 in for cream paper, 0.002252 in for standard color and 0.002347 in for premium color. Spine text is only supported from 79 pages up, and you should leave a small margin inside the spine.
FAQ
Is a page the same as a sheet?
No. Page count means printed pages (both sides of a sheet), as KDP counts them.
Does this work for hardcovers?
No, these values are for paperbacks. Check KDP’s hardcover guidelines separately.
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Estimates only. Always confirm figures in your KDP dashboard.