KDP Spine Width Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter your book's total page count (count every page, not sheets).
- Press Calculate to see the spine width for each KDP paper type, in inches and millimetres.
- Use the figure for the paper you selected when setting up your paperback.
How it works
A paperback spine is simply the page count multiplied by the thickness of one page, which depends on the paper stock: spine width = pages × per-page thickness.
Amazon KDP uses fixed per-page thicknesses: 0.002252 in for black & white or standard colour on white paper, 0.0025 in for cream paper, and 0.002347 in for premium colour. Multiply by 25.4 to convert inches to millimetres.
Worked example
A 300-page book on white paper. Spine width = 300 × 0.002252 = 0.676 in, which is about 17.16 mm.
Tips
- Count the total pages in your interior file, including blanks — not the number of sheets.
- Choose the row that matches the paper type you picked during paperback setup.
Frequently asked questions
Why does my cover template show a slightly different number?
Always trust the exact template KDP generates for your specific trim size and page count. This calculator gives the spine width itself; the template also adds bleed and wrap.
Does KDP put text on every spine?
No. KDP only allows spine text once a book reaches 79 pages, because thinner spines can't print text reliably.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.