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ISBN specifications are available from:
American National Standards Institute (ANSI)
11 West 42nd Street, 13th Fl.
New York, New York 10036
Tel. 212.642.4900
www.ansi.org
document ISO 2108:1992
The last character in a UPC-A, UPC-E, UPC-E1, EAN-13 or EAN-8 bar code
is the checksum. For reference, these are the methods of calculation:
Checksum calculation for UPC-A, EAN-13 and EAN-8
Use Worth Data’s phone number (it's not a real UPC-A code) as sample data:
18314589938
Assign even and odd positions, starting at the right and moving left:
8 3 9 9 8 5 4 1 3 8 1
odd even odd even odd even odd even odd even odd
1. Starting with the leading digit, 8, take the sum of all the characters in
the odd positions.
8 + 9 +8 + 4 + 3 + 1 = 33
2. Multiply the result of step 1 by 3.
33 x 3 = 99
3. Now take the sum of all the even-position characters.
3 + 9 + 5 + 1 + 8 = 26
4. Add the result in Step 2 to the result in Step 3.
99 + 26 = 125
5. Subtract the result from the next higher multiple of 10.
Next higher multiple of 10 over 125 = 130
130 - 125 = 5
5 is the Modulo-10 check character. The data to be printed
becomes:
183145899385.
This same formula is used for EAN-13 (using the 1-12 digits) and EAN-8
(using the 1-7 digits).