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ISBN Validator

Check whether an ISBN-10 or ISBN-13 is valid, see the expected check digit, and convert it to a correctly formatted ISBN-13 and ISBN-10.

Mode

Check an ISBN

Hyphens, spaces and an "ISBN" label are ignored. Nothing is sent anywhere.

Result

Pass: ValidThis is a valid ISBN-13.

Type
ISBN-13
13 characters after cleaning
Cleaned
9781861972712
Check digit
Expected 2
Found 2, matches
Prefix
978

ISBN-13

978-1-86197-271-2

ISBN-10

1-86197-271-7

About the ISBN Validator

An ISBN with one wrong digit can send readers, retailers and libraries to the wrong book or to nothing at all. Every ISBN ends in a check digit calculated from the other digits, which makes most typing errors detectable. This validator runs that check instantly and tells you exactly what is wrong.

Enter an ISBN with or without hyphens, spaces or an "ISBN" label. You will see whether it is valid, whether it is an ISBN-10 or ISBN-13, the cleaned digits, the check digit that was expected against the one that was found, and both formats: the hyphenated ISBN-13 and, for 978 ISBNs, the matching ISBN-10. Each has its own Copy button. Batch mode checks many ISBNs at once and gives you a table and CSV download.

Hyphen placement depends on registration group ranges published by the ISBN agency. This tool includes the ranges for the English language groups 978-0 and 978-1, so those are hyphenated exactly. For other groups, including all 979 ISBNs, it separates the prefix and check digit only. To reformat a whole list, use the ISBN Formatter.

How It Works

Hyphens, spaces, dots and an ISBN label are stripped. Exactly 10 or 13 characters must remain: an ISBN-10 is nine digits plus a digit or X, and an ISBN-13 is 13 digits starting with 978 or 979.

ISBN-10 check digit: multiply the first nine digits by 10 down to 2, add them up, and take what is needed to reach a multiple of 11 (10 is written X). ISBN-13 check digit: multiply digits alternately by 1 and 3, add them up, and take what is needed to reach a multiple of 10.

Conversion from ISBN-10 to ISBN-13 adds 978 in front of the first nine digits and calculates a new check digit. Only 978 ISBN-13s have an ISBN-10 equivalent.

Formula

ISBN-13 check digit
Check = (10 − (Σ digitᵢ × weightᵢ mod 10)) mod 10, weights 1, 3, 1, 3…
ISBN-10 check digit
Check = (11 − (Σ digitᵢ × (10 − i) mod 11)) mod 11, where 10 = X

Example

Checking 978-1-86197-271-2 and a mistyped copy

  1. 978-1-86197-271-2 cleans to 9781861972712, a 13-digit ISBN starting with 978.
  2. The weighted sum of the first 12 digits gives an expected check digit of 2, which matches.
  3. Converted to ISBN-10: 1-86197-271-7 (new check digit 7).
  4. Typed as 9781861972713, the same ISBN fails: the check digit should be 2, not 3.

978-1-86197-271-2 is a valid ISBN-13 whose ISBN-10 is 1-86197-271-7.

Important Notes

  • A valid check digit means the number is well formed. It does not confirm the ISBN has been assigned or which book it belongs to.
  • Exact hyphenation covers 978-0 and 978-1 only. Other groups show a prefix-separated form, which is still the correct number.
  • Missing digits are never guessed. An incomplete ISBN is reported as an error.
  • Free KDP ISBNs are valid ISBN-13s that start with 979 in many cases; they have no ISBN-10 form.

Frequently Asked Questions

Is an ISBN-10 still valid?

Yes, older ISBN-10s remain valid identifiers, but the book trade has used ISBN-13 since 2007. Use the ISBN-13 on covers, barcodes and KDP.

Why does my 979 ISBN have no ISBN-10?

ISBN-10 only existed for the 978 range. ISBNs that begin with 979 were created after the switch to 13 digits and have no 10-digit equivalent.

My ISBN fails the check. What should I do?

Compare it digit by digit with your assignment from your ISBN agency or KDP. The usual causes are a mistyped digit or two swapped digits. Do not just change the last digit, since the error may be elsewhere.

Do hyphens matter?

No, they are only for readability. 9781861972712 and 978-1-86197-271-2 are the same ISBN. KDP generally asks for the ISBN without hyphens.

Why are some ISBNs only partly hyphenated?

Correct hyphen positions depend on registrant ranges that differ for every group. This tool has the ranges for 978-0 and 978-1 built in. For other groups it shows the prefix and check digit separated rather than guess.

Can I check a whole list?

Yes. Switch to Batch check, paste ISBNs one per line and download the results as CSV.

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