Container Check Digit Calculator

Our ISO Container Check Digit Calculator is easy and free to use. Simply enter your container number in the field below and it will calculate the check digit according to ISO 6346:1995 for that container.

Check Digit:
Prefix Number:
Serial Number:
Container Number:

All containers used for international container shipping, including tank containers, must have a unique container number. This unique number is made up of the following:

1. Four letter prefix; the first three letters show the identity of the owner and the fourth is always the letter 'U' which is identifying the unit as a container. This is known as a BIC code.
2. Six digit serial number; this six digit number is contrived and designated by the owner.
3. Single check digit; this single check digit is there to pick up any errors which might be caused by incorrect transcription of the registration number.

If you have a wrong check digit you have an invalid container number, it does not matter where in the world you are, if you have an invalid container number it is impossible to trace the container through the sea freight shipping process.

Please start by entering the four digit prefix number which relates to the container owner code plus the letter 'U' and then the six digit container serial number to calculate the check digit therefore supplying the full shipping container number.