ISBN Converter
NewValidate and convert between ISBN-10 and ISBN-13, with check-digit verification and hyphenated formatting.
————Hyphenation here follows the common EAN prefix / group / publisher / title / check-digit layout for illustration — the registration-group and publisher-range boundaries are approximated, not looked up from the official ISBN agency ranges.
Frequently Asked Questions
How is the ISBN-10 check digit calculated?
Each of the first 9 digits is multiplied by a descending weight from 10 down to 2, the products are summed, and the check digit is whatever value (0-9, or "X" for 10) makes the total sum divisible by 11.
How is the ISBN-13 check digit different?
ISBN-13 uses the EAN-13 barcode checksum: the first 12 digits are alternately multiplied by 1 and 3, summed, and the check digit is whatever value makes that sum a multiple of 10 — the same algorithm used for retail barcodes generally.
How does converting ISBN-10 to ISBN-13 work?
The "978" EAN Bookland prefix is prepended to the first 9 digits of the ISBN-10, and a fresh ISBN-13 check digit is computed for that 12-digit string — the original ISBN-10 check digit is discarded since it used a different algorithm.
Why can't every ISBN-13 convert back to an ISBN-10?
ISBN-10 only exists within the "978" (Bookland) EAN prefix. Newer books assigned a "979" prefix ISBN-13 have no ISBN-10 equivalent at all, since that numbering space was created specifically because 978 numbers were running out.
Is the hyphenation shown official?
No — official ISBN hyphenation depends on registration-group and publisher-range tables maintained by the International ISBN Agency. The hyphenation shown here approximates the typical prefix/group/publisher/title/check-digit layout for readability, not an authoritative lookup.