ISBN-10 / ISBN-13 Converter
Convert a single ISBN or a batch of ISBNs between the 10-digit and 13-digit formats. The tool auto-detects the format, validates the check digit, and shows the calculation.
Single ISBN Converter
Hyphens and spaces are ignored automatically.
Batch Converter
ISBN-10 and ISBN-13 Explained
ISBN stands for International Standard Book Number. It is the universal identifier for books and book-like products, assigned to each distinct edition of a title. ISBNs are managed by the International ISBN Agency and assigned through national agencies in each country.
ISBN-10 was the original format — 10 characters long (9 digits plus a check character that can be 0–9 or X, where X represents 10). ISBN-10 has been officially superseded since January 2007 but remains in wide use in library catalogs, older databases, and bibliography tools.
ISBN-13 is the current international standard, aligned with the EAN-13 barcode format. All ISBN-10 numbers have an ISBN-13 equivalent formed by prepending 978 and recalculating the check digit. New books issued after 2007 may also have 979 as the prefix — these have no ISBN-10 equivalent.
Check Digit Formulas
ISBN-10 Check Digit
Multiply each of the first 9 digits by a decreasing weight from 10 to 2, sum the products, then calculate:
// If result is 10, use "X"
ISBN-13 Check Digit
Multiply each of the first 12 digits by alternating weights of 1 and 3, sum the products, then calculate:
Frequently Asked Questions
Can I convert any ISBN-13 to ISBN-10?
Only ISBN-13 numbers that start with 978 have an ISBN-10 equivalent. Numbers starting with 979 were introduced to expand the ISBN pool and have no ISBN-10 counterpart — there are simply not enough 10-digit combinations to accommodate the full 979 range.
Why does "X" appear in some ISBN-10 numbers?
The ISBN-10 check digit formula can produce a result of 10, which cannot be represented as a single digit. The letter X (Roman numeral for 10) is used as a placeholder in that position. ISBN-13 check digits are always a single digit (0–9).
Are hyphens part of the ISBN?
Hyphens are separators used for readability (dividing the ISBN into prefix, registration group, registrant, publication, and check digit). They are not part of the numerical value and can be in different positions for different publishers. This converter ignores hyphens and spaces during conversion. If you're embedding an ISBN in a URL query string, the URL Encoder will handle any special characters safely.
What is an ISSN? How does it differ from an ISBN?
An ISSN (International Standard Serial Number) identifies periodicals — magazines, journals, and newspapers — using an 8-digit format. An ISBN identifies individual book editions. They serve different purposes and are not interchangeable.
