Code 128 Barcode Check Digit

Code 128 barcodes have a mandatory check digit. This calculated checksum is based on the value associated with each Code 128 character. The character values are in the left hand column of this table. The stop bar is not included in this check digit calculation.

The check digit is calculated by adding the value of the start character to each character's value, multiplied by its ordinal position in the string. The subtotal is divided by 103. The check digit is the character associated with the remainder.

The check character's value = startBarValue(individualCharacter'sValue * positionInTheStringL-R) / mod 103