Barcode Checksum Calculator

Some barcodes carry a hidden checksum so a scanner can tell it misread. Code 128 always has one (modulo 103); Code 39 has an optional one (modulo 43); MSI usually uses modulo 10; Luhn is used for IMEI and card numbers. Pick the method, type the data, and see the check value with the working.

Barcode software adds the Code 128 check symbol for you. This is useful to verify a printed code, to understand a scanner's raw output, or to add the optional Code 39 check character before you make the barcode with the Code 39 or Code 128 generator. For EAN, UPC and ISBN see the check digit calculator.