ISBN-10 to ISBN-13 Converter

Books published before 2007 carry 10-digit ISBNs; since then the ISBN has 13 digits and doubles as the EAN-13 barcode number. This converter turns ISBN-10 into ISBN-13 and back, verifies the check digit of every number first, and handles whole lists — paste one ISBN per line, up to 400 at a time.

How to use this tool

1. Paste one or more ISBNs, one per line. Hyphens, spaces and an “ISBN” prefix are fine.
2. Leave the direction on Auto, or force conversion to ISBN-13 or ISBN-10.
3. Copy the result; for a list, use the table or the one-per-line output. Lines with problems show the reason.

Formula

ISBN-13 = 978 + first nine digits of the ISBN-10 + new check digit, where check = (10 − (d1 + 3·d2 + d3 + … + 3·d12) mod 10) mod 10

The ISBN-10 check character is c = (11 − (10·d1 + 9·d2 + … + 2·d9) mod 11) mod 11, written X when c is 10. Converting back drops the 978 prefix and recomputes that mod-11 check. Only 978 numbers can go back: ISBNs starting with 979 were never issued in a 10-digit form.

Example

For 0-306-40615-2, drop the final 2 and add 978 to get 978030640615. Its weighted sum is 9 + 21 + 8 + 0 + 3 + 0 + 6 + 12 + 0 + 18 + 1 + 15 = 93, so the check digit is 7 and the ISBN-13 is 9780306406157 (hyphenated 978-0-306-40615-7). Converting 9780306406157 back gives 0306406152. A 979 number such as 979-10-90636-07-1 is valid — its first twelve digits weigh 129, so the check digit is 1 — but it has no ISBN-10.