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ISBN Validator

Check whether an ISBN is valid and find its check digit.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

This calculator validates International Standard Book Numbers by recomputing their check digit — ISBN-10 uses a weighted sum with weights 10 down to 1, mod 11 (the result can be the letter X), while ISBN-13 uses alternating weights of 1 and 3 mod 10, the same scheme as EAN/UPC barcodes. It flags whether the entered number's check digit matches what the algorithm predicts.

Librarians, booksellers, and publishing or cataloging software use this check to catch typos before a book record is entered into a database or an ISBN is printed on a cover. Enter any ISBN-10 or ISBN-13 to see whether it's valid and what its correct check digit should be.

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