ISBN checker

1. Enter an ISBN with or without hyphens and spaces.
2. Read whether it is valid and which format it is.
3. See the matching ISBN-10 or ISBN-13 where one exists.
4. Enter only the first digits to get the missing check digit.

An ISBN-13 has 13 digits. Each digit is multiplied by 1 or 3 in turn, the products are added, and the sum must be a multiple of 10. An ISBN-10 uses weights from 10 down to 1 and the sum must be a multiple of 11, where the last character can be X for ten.

To convert ISBN-10 to ISBN-13, add 978 to the front, drop the old check digit and calculate a new one. Only ISBN-13s that begin with 978 can be converted back to ISBN-10.

• A valid check digit does not prove the ISBN was issued to you. Real ISBNs come from your national ISBN agency, such as isbn.org in the United States.
• Each format of a book needs its own ISBN: paperback, hardcover, ebook and audiobook.
• This tool does not look up titles or owners.

These free utilities from SEO Site Checker, a separate site, pair well with this tool: QR Code Generator. Check their terms before uploading anything private.

Use the tools together, starting with word count and ending with keywords. See every tool on our free author tools page.

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A calculator gives you a number, and our team does the work behind it. Get a free consultation and we will quote the editing, design, formatting and publishing in writing before any work starts.