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.
Spine width by page count
| Pages | White paper | Cream paper |
|---|---|---|
| 100 | 0.2252 in (5.72 mm) | 0.2500 in (6.35 mm) |
| 150 | 0.3378 in (8.58 mm) | 0.3750 in (9.52 mm) |
| 200 | 0.4504 in (11.44 mm) | 0.5000 in (12.70 mm) |
| 250 | 0.5630 in (14.30 mm) | 0.6250 in (15.88 mm) |
| 300 | 0.6756 in (17.16 mm) | 0.7500 in (19.05 mm) |
| 350 | 0.7882 in (20.02 mm) | 0.8750 in (22.22 mm) |
| 400 | 0.9008 in (22.88 mm) | 1.0000 in (25.40 mm) |
| 450 | 1.0134 in (25.74 mm) | 1.1250 in (28.57 mm) |
| 500 | 1.1260 in (28.60 mm) | 1.2500 in (31.75 mm) |
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.
- What is the spine width of a 200-page book?
- On white paper a 200-page paperback has a spine of 0.4504 inches (11.44 mm); on cream paper 0.5 inches (12.70 mm). A 400-page book is 0.9008 inches on white and 1 inch on cream.
- Does colour printing change the spine width?
- Slightly. Amazon KDP's per-page figures are 0.002252 inches for standard colour (the same as white paper) and 0.002347 inches for premium colour, so a 300-page premium colour book has a 0.7041 inch spine.
- How big is the full cover file?
- Back cover, spine and front cover side by side, plus 0.125 inches of bleed on each outer edge; the height is the trim height plus 0.125 inches top and bottom. For a 6 × 9 inch, 300-page book on white paper that is 12.926 × 9.25 inches.
- 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 17 October 2026. Check the source before you rely on a number for a print order.
If you would rather have it done for you, ask for a free consultation call or see the packages and prices. The spine width is one measurement of a print cover: see our book cover design services, or work out the length first with the word count to page count calculator.
Written by the Harmony Publishing Editorial Team. More free tools.