What is a container check digit? And what is it used for?

A check digit is used to detect errors in an intermodal shipping container number. The seventh digit of the container number also known as the check digit, is calculated off of the four letters and six digits of the container number. As long as the container number follows the ISO standard, the container number can be entered into a check digit calculator to determine if it is a valid number.

Verify Multiple Container Numbers or Calculate a Container Check Digit

Example of Check Digit Verification

Example of Check Digit Calculation