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The following formulas are taken from the Machine-Readable Coding Guidelines for the US Book Industry.
Checking the Bookland EAN
1. Assign the constant weighting factors associated with each position in the EAN. (Alternating 1 and 3. See the table in step 2.)
2. Multiply each digit by its associated weighting factor and add together. For example, calculations for EAN 9780901690548 would be:
| Weighting Factors |
1 |
3 |
1 |
3 |
1 |
3 |
1 |
3 |
1 |
3 |
1 |
3 |
1 |
|
| Bookland EAN |
9 |
7 |
8 |
0 |
9 |
0 |
1 |
6 |
9 |
0 |
5 |
4 |
8 |
|
| Values (product) |
9 + |
21 + |
8 + |
0 + |
9 + |
0 + |
1 + |
18 + |
9 + |
0 + |
5 + |
12 + |
8 = |
100 |
3. Divide the sum by the number 10 and the result must be a whole number with no remainder.
Calculating the check digit for the ISBN
1. Remove the first three digits (978) and the last digit from the Bookland EAN. (The last digit is the Bookland EAN check digit.) You are left with a nine digit number. For example, EAN 9780940016610
becomes 094001661.
2. Multiply each digit by its associated weighting factor and add
together. For example, calculations for 094001661 would be:
| Weighting Factors |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
|
| ISBN |
0 |
9 |
4 |
0 |
0 |
1 |
6 |
6 |
1 |
|
| Values (product) |
0 + |
81 + |
32 + |
0 + |
0 + |
5 + |
24 + |
18 + |
2 = |
162 |
3. Divide the sum by the number 11. (162/11 = 14 with 8 remainder)
4. Subtract the remainder, if any, from 11 to get the check digit (11 - 8 = 3).
If the result is 0 the check digit is 0. If the check digit is 10, it is represented by the Roman numeral X. The final ISBN in our example is 0-940016-61-3.
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