# ISBN Decoded: Compliance??

There are several (confusing, complicated, and time-consuming) compliance requirements for a printed, saleable book to be, well...saleable. The most important requirement is obtaining an International Standard Book Number, or ISBN. (Not “ISBN number” or “izbin." Just ISBN, please.) This number gives your book a universal numerical identifier—sort of a Social Security number for your work. It lasts for the life of the book and allows bookstores, media, publishers, and consumers to order, identify, and refer to your book. In fact, almost all major ordering systems use the ISBN exclusively

ISBNs formerly consisted of ten digits, but the International ISBN Agency changed the system to use a thirteen-digit number because they were running out of ten-digit numbers. Every thirteen-digit ISBN contains five sets of numbers, each separated by dashes.

Lets decode those digits, shall we?

The first three digits are 978, the default prefix for books. When all of the current ISBNs are used, the next prefix will be 979.

The next section may be up to five digits and identifies the country, region, or language of the book; a 0 or 1 means the book is published in English. In the example, it is a 1.

The third series describes the publisher or imprint and is usually six or seven digits long—the publisher number in the example is 929774. These three sets of numbers together comprise your ISBN prefix.

The fourth set is the publication number. Usually, a 0 or 00 is used for the first book by a particular publisher, then a 1 or 01 for the second, and so on. The example’s publication number is 38, meaning it’s the thirty-ninth book released by the publisher who owns the corresponding prefix.

The final digit is the check digit, which can be a numeral from 0 to 9 or the letter *X*. It is calculated on a modulus 11 with weights of 10 through 2, using X in lieu of 10 where ten would occur as a check digit. Did we lose you? Basically, using an automatic algorithmic calculation (we like to call it magic), this digit acts as a check to make sure the entire ISBN is correct. The check digit in the example is an 8.

And that’s your ISBN in a nutshell!

If we’ve piqued your interest in ISBNs, visit R. R. Bowker, the official ISBN agency in the United States. There you can convert your ten-digit ISBN to a thirteen-digit ISBN, register a new ISBN, and more.