Spine Width and Cover Size
Spine width is page count multiplied by paper thickness, which is why cream books are visibly fatter than white ones at the same length. Build the cover only once the interior is final: one added page changes the spine and shifts the whole wrap.
Spine width
0.450 in
Full cover, with bleed
12.700 x 9.250 in
Spine width is page count multiplied by paper thickness: 0.002252 inches a page for white, 0.0025 for cream, 0.002347 for premium colour. Cream is about eleven percent thicker, so the same manuscript on cream needs a visibly wider spine.
The full wraparound adds the back cover, the front cover and 0.125 inches of bleed on every outer edge. Build it only after the interior is final: a single added page changes the spine and shifts the whole design. KDP also refuses spine text under 79 pages, because there is not enough width to print it reliably.
Rates are Amazon.com (US) figures, checked against KDP's own published examples on 25 August 2026. Amazon changes these without notice and they differ by marketplace, so confirm in your KDP dashboard before you commit to a price.
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