Book Spine Width Calculator
Exact spine width from page count and paper type
The spine is the one cover measurement you cannot guess. Get it wrong by a couple of millimetres and your title sits off-centre or wraps onto the front. Spine width is page count multiplied by a per-page thickness that depends on the paper stock your printer uses.
How do you calculate spine width?
Multiply your total page count by the paper thickness for your stock. On Amazon KDP, white paper is 0.002252 inches per page, cream is 0.0025 inches, and colour is 0.002347 inches. A 300-page book on white paper is 300 x 0.002252 = 0.6756 inches.
Does page count mean sheets or sides?
Pages, not sheets. Every side counts. A book that is 150 sheets of paper is 300 pages, and 300 is the number you feed into the formula. Always use the final page count from your formatted interior file, including blank pages.
Why is there a minimum page count for a spine?
KDP will not print spine text on books under 79 pages, because the spine is too narrow to hold type reliably. Below that threshold, design the cover with no spine text at all rather than risking a misaligned print.
How much tolerance should I leave?
Printers allow a shift of about 0.0625 inches (1.6 mm) in either direction. Keep spine text at least 0.0625 inches away from both folds, and avoid tight boxes or borders on the spine, since a small shift makes them look crooked.
Frequently asked questions
How wide is the spine of a 300 page book?
On KDP white paper a 300-page book has a spine of about 0.676 inches (17.2 mm). On cream paper the same book is 0.75 inches (19.1 mm).
What is the KDP paper thickness per page?
White paper is 0.002252 inches per page, cream is 0.0025 inches per page, and colour is 0.002347 inches per page.
Can I put text on the spine of a thin book?
Only if the book has 79 or more pages. Below that, KDP requires a blank spine.
Is spine width different for hardcover?
Yes. Hardcovers add board and wrap thickness, so the spine is wider than the paper stack alone. Use your printer's hardcover template rather than the paperback formula.
Does spine width change between KDP and IngramSpark?
Yes, slightly, because their paper stocks differ. Always generate the cover template from the printer you are actually using.