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ISBN Converter & Validator
Enter an ISBN-10 or ISBN-13 to check its check digit and get the other format instantly, with hyphens. Paste a list to convert hundreds of ISBNs at once and download the results as CSV.
Last updated:
Mode
Hyphens, spaces and an 'ISBN' prefix are ignored.
Enter your values to see the result.
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How to use the ISBN Converter & Validator
- Choose single or bulk mode.
- Type or paste an ISBN, with or without hyphens, or one ISBN per line.
- Click Convert (results also update as you type).
- Check the verdict and copy the ISBN-10 or ISBN-13 you need.
- In bulk mode, download the conversion table as CSV.
ISBN check digit formulas
| ISBN-10 | ISBN-13 | |
|---|---|---|
| Weights | 10, 9, 8, 7, 6, 5, 4, 3, 2 (check digit has weight 1) | 1, 3, 1, 3 … alternating |
| Check digit | (11 − sum mod 11) mod 11, 10 → X | (10 − sum mod 10) mod 10 |
| Valid when | sum of all 10 weighted digits is divisible by 11 | sum of all 13 weighted digits is divisible by 10 |
| Example | 0-306-40615-2 | 978-0-306-40615-7 |
Parts of an ISBN
| Part | Example (978-0-306-40615-7) | Meaning |
|---|---|---|
| Prefix | 978 | EAN "Bookland" prefix, 978 or 979 (ISBN-13 only) |
| Registration group | 0 | Language area or country (0 and 1 = English, 2 = French, 3 = German, 4 = Japan, 7 = China…) |
| Registrant (publisher) | 306 | Publisher or imprint code |
| Publication | 40615 | The specific edition and format |
| Check digit | 7 | Detects typing errors |
Each edition and format (hardback, paperback, e-book) gets its own ISBN. Since 2007 all new ISBNs are issued as 13 digits; ISBN-10 is still printed on many older books.
Frequently asked questions
How do I convert an ISBN-10 to ISBN-13?
Remove the ISBN-10 check digit, put 978 in front of the remaining 9 digits and calculate a new check digit with the ISBN-13 (EAN-13) rule. For example 0-306-40615-2 becomes 978-0-306-40615-7.
How is the ISBN-13 check digit calculated?
Multiply the first 12 digits alternately by 1 and 3, add them up, and the check digit is (10 − sum mod 10) mod 10. For 978030640615 the weighted sum is 93, so the check digit is 7.
How is the ISBN-10 check digit calculated?
Multiply the first nine digits by 10, 9, 8 … 2, add them, and the check digit is (11 − sum mod 11) mod 11. A result of 10 is written as the letter X.
Can every ISBN-13 be converted to ISBN-10?
No. Only ISBN-13s starting with 978 have an ISBN-10 equivalent. ISBNs with the 979 prefix, now used in France, Korea, Italy, Spain and the United States, exist only as 13 digits.
Is the ISBN-13 the same as the barcode number?
Yes. The ISBN-13 is the EAN-13 number printed under a book's barcode, which is why it starts with the 978 or 979 'Bookland' prefix.
Why are the hyphens in different places for different books?
The parts (prefix, registration group, publisher, title, check digit) vary in length; large publishers get short codes and more title numbers. Exact positions come from the International ISBN Agency range table. This tool knows the full publisher ranges for English-language groups 0 and 1 and hyphenates other numbers at the registration group.
Does a valid ISBN mean the book exists?
No. The check digit only catches typing errors. A number can be valid but not assigned to any book.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
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