How is the Mod10 check digit calculated?

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The last digit in the Type 1 bar code format is called the "check digit" and the program calculates it automatically. You do not need to enter this digit. ResourceMate® uses a Mod 10 check digit and this is how it is calculated:

Starting from the left, multiply all the digits in the odd numbered positions by 2 and the digits in the even numbered positions by 1.
If the result of a multiplication of a single digit by 2 results in a two-digit number (say "7 x 2 = 14"), add the digits of the result together to produce a new single-digit result ("1+4=5").
Add all single-digit results together.
The check digit is the amount you must add to this result in order to reach the next highest multiple of ten. For instance, if the sum in step #3 is 22, to reach the next highest multiple of 10 (which is 30) you must add 8 to 22. Thus the check digit is 8.

Here is an example for the bar code of 3005600008000 (without check digit):

Original bar code #	3	0	0	5	6	0	0	0	0	8	0	0	0
Multiply digits by	2	1	2	1	2	1	2	1	2	1	2	1	2
Initial results:	6	0	0	5	12	0	0	0	0	8	0	0	0
Reduce each to one digit:	6	0	0	5	3	0	0	0	0	8	0	0	0

Add all resulting digits: = 22

Amount to reach next 10: = 22 + 8 = 30

Thus, mod 10 check digit is 8. The final 14-digit bar code number will be 30056000080008.

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