required to split the ISBN into its constituent parts follows below. See 

Check digit

 section

for information regarding check digit calculation and validation.

The number of digits in each of the ISBN elements for registration group, registrant, and

publication varies in length, although the number of digits contained in these three

elements is nine in total. These nine digits, together with the three digit prefix element and

the check digit, make up the 13 digit ISBN. The number of digits in the registration group

and registrant elements will vary according to the publishing output of the registration

group or registrant in question. Registration groups for which large output of monographic

publications is anticipated will receive group numbers of one or two digits. Publishers with

an expected large output of publications will be assigned registrant numbers of two or

three digits. 

Note:

 The number of digits specified and assigned for registrant groups and registrants

within prefix element 978 cannot be relied upon to predict those which are specified and

assigned within future prefix elements (e.g., prefix element 979). Registration groups and

registrant allocations for future prefixes will reflect assignment history and assignment

projections for the entire prefix element system viewed collectively.

Determining the internal divisions of the 13 digit ISBN is a two step process: first,

determine the registration group using the rules for prefix elements assigned for ISBN;

second, determine the registrant and publication element lengths using the registration

group rules. Registration group rules are available from the International ISBN Agency.

Table 1 illustrates the distribution of registration group ranges within prefix element 978.

Any other EAN.UCC prefix defined for use within the ISBN system will have registration

group rules available from the International ISBN Agency prior to any registration group

assignment within that EAN.UCC prefix. 

It is strongly

recommended to check with the

International ISBN Agency on a regular basis for possible additions or changes to

registration group rules.

Table 1: Distribution of registration group ranges within prefix element 978

Prefix element

Registration Group Numbers available per Registration Group

element range

978

0 

5

100,000,000

6

(undefined range)

7

100,000,000

80 

94

10,000,000

950 

989

1,000,000

9900 

9989

100,000

99900 

99999

10,000

Table 2 illustrates how to derive the registration group structure for prefix element 978 that

is assigned for an ISBN. An examination of the five digits following the prefix element will

permit the determination of the length of the registration group element. Once the

registration group length is known, the registrant group can be derived.

Table 2: Method of deriving the registration group structure for prefix element 978

If the five digits

Registration Group

The prefix element and Registration

following the prefix 

length is:

Group divisions would occur after 

12