ISBNs are assigned, not simply converted. For editions published before the year 2007, 10 digits are assigned, including the check digit which is the 10th. Conversely, 13 digits are assigned for editions published starting in the year 2007. The 13th digit is the check digit. GS1 allocates the prefixes 978-979 for editions published starting in year 2007. To legally convert 10-digit ISBN to 13-digit ISBN, a revised edition, not simply a reprint, thereof must be published starting in the year 2007. The publisher applies for ISBN, which may have a prefix of either 978 or 979, starting in the year 2007.
@Twifoo , so all this bunch of ISBN10=>13 converters on the web (not only Excel formulas) are just "faking" info and we shall ignore them? My understandig was what for existing before 2007 publications not totally new ISBN13 assigned, but converted by some algorithm from ISDN10.
They had a misconception that just because a book, which was published before 2007 and assigned with IBSN-10, can now be automatically be converted to IBSN-13. To legally do that, the book has to be revised and published after 2007. Also, the prefix is not always 978. It may also be 979, such that any ISBN-13 must always be unique. A hard bound book will be assigned ISBN-13, which will be different from the same book published as ebook. I am a sole author of several accounting textbooks. My latest revision will be entitled EXCELlent Financial Accounting and Reporting. So, I must know ISBNs.