Book Spine Width Calculator
Enter your page count, paper GSM, paper type, and binding below. The calculator works out the text block thickness and total spine width in mm and inches — so your cover artwork fits perfectly.
How the calculator works
The spine width is determined by the thickness of the text block (all your pages stacked together). Each sheet of paper contributes a small amount based on its GSM (grams per square metre). Coated papers are typically 25% thinner than uncoated at the same GSM because the coating compresses the fibres. For a hardcover book, the rigid boards and casing add approximately 4 mm on top of the text block.
The per-sheet thickness values used are: 70 GSM = 0.088 mm, 75 GSM = 0.094 mm, 80 GSM = 0.10 mm, 90 GSM = 0.112 mm, 100 GSM = 0.125 mm, 120 GSM = 0.15 mm (uncoated). Coated values are multiplied by 0.75.
Frequently Asked Questions
How do I calculate book spine width?
Divide the page count by 2 to get sheets, multiply by the per-sheet thickness for your paper GSM, then add 4 mm for hardcover boards if applicable. For example, 200 pages on 80 GSM uncoated paper = 100 sheets × 0.10 mm = 10.0 mm spine.
What is spine width for 100 pages?
For 100 pages (50 sheets) on standard 80 GSM uncoated paper with perfect binding, the spine is approximately 5.0 mm (0.20 in). The exact value depends on GSM and whether the paper is coated.
Does GSM affect spine width?
Yes. Higher GSM paper is thicker per sheet, so the same page count on 120 GSM paper produces a noticeably wider spine than on 70 GSM paper. Coated paper is also ~25% thinner than uncoated at the same GSM.
What is the minimum pages for perfect binding?
Perfect (soft cover) binding is generally recommended for books with at least 32 pages (16 sheets). Fewer pages produce a spine too thin to glue securely, and the book may fall apart quickly.
How is hardcover spine different from perfect binding spine?
A hardcover spine adds approximately 4 mm to the text block thickness to account for the rigid boards and casing material. Use our calculator and select Hardcover to see the adjusted spine width.
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Also see: all binding types · official price calculator