BYTETOOLS

ISBN Validator & Converter

Validate an ISBN check digit, convert between ISBN-10 and ISBN-13, add the correct hyphens and check a whole list at once with a pass or fail column.

Enter an ISBN above to validate its check digit and convert between ISBN-10 and ISBN-13.

A valid check digit proves the number is well formed, not that the ISBN has been assigned to a real book. Everything runs in your browser — no ISBN you type is sent anywhere.

What is the ISBN Validator & Converter?

An ISBN carries its own check digit, so a typo in a catalogue record, a cover file or a distributor spreadsheet can be caught without looking anything up.

  • Validates ISBN-10 with the mod 11 weighted sum and ISBN-13 with 1 and 3 weights
  • Converts between ISBN-10 and ISBN-13 and recomputes the check digit
  • Hyphenates using registration-group and registrant range tables
  • Names the registration group, such as English language or Spain
  • Bulk mode with a pass or fail column and a CSV copy of the results
  • Says exactly which check digit was expected when a number fails

How to use the ISBN Validator & Converter

  1. 1

    Choose whether to check a single ISBN or a whole list of them.

  2. 2

    Type or paste the number — hyphens, spaces and dashes are ignored.

  3. 3

    Read the pass or fail verdict and compare the expected check digit with the one supplied.

  4. 4

    Copy the ISBN-13, ISBN-10 and hyphenated forms, or copy the bulk results as CSV.

About the ISBN Validator & Converter

An ISBN carries its own check digit, so a typo in a catalogue record, a cover file or a distributor spreadsheet can be caught without looking anything up. This tool recomputes that digit for both formats — mod 11 with X allowed for ISBN-10, alternating weights of 1 and 3 for ISBN-13 — and tells you which digit it expected.

Valid numbers are converted between the two formats and hyphenated properly, using the registration-group and registrant range tables rather than guesswork, so the dashes land where the ISBN agency puts them. The registration group is named as well. Bulk mode checks a whole pasted list and gives every line a pass or fail with a CSV copy.

Hyphens, spaces and every flavour of dash are stripped before checking, so numbers can be pasted in any format. Everything runs in your browser and no ISBN you enter is sent anywhere. Do bear in mind that a valid check digit proves the number is well formed, not that it has been assigned to a real book.

Frequently asked questions

How do you check if an ISBN is valid?

Recompute the final check digit from the preceding digits and compare it with the one printed. ISBN-10 uses a weighted sum modulo 11 where a remainder of ten is written as X; ISBN-13 uses alternating weights of 1 and 3 modulo 10.

Can every ISBN-13 be converted to an ISBN-10?

No. Only ISBN-13s that begin with the 978 prefix have an ISBN-10 equivalent, because the ISBN-10 is simply that number with the prefix dropped and the check digit recalculated. Numbers starting 979 have no ten-digit form at all.

What does the X at the end of an ISBN mean?

It is the ISBN-10 check digit for the value ten, which cannot be written as a single decimal digit. It only ever appears in the last position of a ten-digit ISBN, never in an ISBN-13, which is digits only.

Why are the hyphens in an ISBN not evenly spaced?

The hyphens separate the EAN prefix, the registration group, the registrant and the publication element, and those parts have variable lengths. A large publisher gets a short registrant number and a long list of titles, so the split moves depending on the number.

Does a valid check digit mean the book exists?

No. The check digit only proves the number is internally consistent and has not been mistyped. Confirming that an ISBN has actually been assigned to a published title requires a lookup in a registry, which this offline tool does not do.

Related tools