Book spine width calculator
A paperback's spine width is its page count multiplied by the thickness of one page: 0.002252 inches on white paper, 0.0025 inches on cream paper (Amazon KDP's published figures). Enter your page count below for the spine width and the full cover size.
How it works
Spine width = page count × the per-page thickness of the paper. The full cover width is the back cover, the spine and the front cover, plus 0.125 in bleed on each outer edge; its height is the trim height plus 0.125 in bleed top and bottom.
The per-page figures are Amazon KDP's: 0.002252 in (white paper and standard colour), 0.0025 in (cream paper) and 0.002347 in (premium colour). A different printer or paper stock gives a slightly different spine, so ask for the exact figure before you finish a cover for printing.
Questions
- How do I calculate spine width?
- Multiply the page count by the paper thickness per page: 0.002252 inches for white paper, 0.0025 inches for cream paper (Amazon KDP's figures). A 300-page book on white paper has a spine of 0.6756 inches.
- How many pages do I need for spine text?
- Amazon KDP advises adding spine text only from 79 pages, and leaving at least 0.0625 inches (1.6 mm) on each side of it.
- Is this the spine width for every printer?
- No. It uses Amazon KDP's published paper thickness. Another printer or paper can differ slightly, so confirm the figure with whoever prints your book.
Sources
Figures checked on 7 October 2026. Check the source before you rely on a number for a print order.
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Written by the Harmony Publishing Editorial Team. More free tools.