Book Spine Width Calculator
Work out your paperback’s spine width and full cover size from the page count, paper and trim size.
Spine factors and page ranges from KDP’s help pages, checked 2026-10-04. Bleed is 0.125 in on the top, bottom and outside edges. Confirm with KDP’s cover calculator before you upload.
How to use the spine width calculator
Enter your page count, then pick the ink and paper and the trim size you chose in KDP. The calculator gives the spine width, the full cover size including bleed (in inches or millimetres, and in pixels at 300 DPI), and whether KDP will print text on your spine.
How spine width is worked out
A paperback spine is as thick as the paper inside it, so spine width = page count × paper thickness. KDP publishes the thickness per page for each paper:
- Black ink on white paper: 0.002252 in per page
- Black ink on cream paper: 0.0025 in per page (cream paper is a little thicker)
- Standard color on white paper: 0.002252 in per page
- Premium color on white paper: 0.002347 in per page
The full cover is one PDF: back cover, spine and front cover side by side, plus 0.125 in of bleed on the top, bottom and outside edges. So a 6 × 9 in book is 0.125 + 6 + spine + 6 + 0.125 inches wide and 9.25 inches tall.
KDP only prints spine text on books with more than 79 pages, and the text needs at least 0.0625 in of space on each side. Thin books often look better with a plain spine colour.
Hardcovers and IngramSpark work differently. KDP doesn’t publish a hardcover spine formula, and IngramSpark’s papers have their own thickness, so take those templates from their own cover tools (linked under the calculator). Before you upload anywhere, download the printer’s template and check your cover against it.
Writing the inside first? See how long an ebook should be and the word count to pages calculator.
Spine width examples
200 pages, white paper, 6 × 9 in
Spine 200 × 0.002252 = 0.450 in. Full cover 12.700 × 9.250 in (3,810 × 2,775 px at 300 DPI), with room for spine text.
120 pages, cream paper, 5.5 × 8.5 in
Spine 120 × 0.0025 = 0.300 in. Full cover 11.550 × 8.750 in. Spine text fits, inside a 0.175 in strip.
60-page workbook, premium color, 8.5 × 11 in
Spine 60 × 0.002347 = 0.141 in. Full cover 17.391 × 11.250 in. Too thin for spine text, so leave the spine plain.
Spine width calculator FAQ
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How do I calculate the spine width of a book?
Multiply the page count by the thickness of one page for your paper. For a KDP paperback on white paper that’s pages × 0.002252 in; on cream paper, pages × 0.0025 in. The calculator does it for every KDP paper.
How many pages do I need for spine text on KDP?
More than 79. KDP doesn’t print spine text on thinner books, and the text needs at least 0.0625 in (1.6 mm) of clear space on each side of the spine.
Does page count include blank pages?
Yes. The page count is every page in your interior PDF, blank ones included, because they all add thickness. Front matter like the title and copyright pages counts too.
What about hardcovers and IngramSpark?
KDP doesn’t publish a hardcover spine formula, and IngramSpark’s spine widths come from its cover template generator. Use their own tools for those; the links are under the calculator.
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