Container knowledge

Container number according to ISO 6346

To create a container marker according to the international standard ISO 6346:

Structure of the container number

Each container receives a globally unique container number, which is clearly visible on both fronts. It consists of the three-digit owner key (letters A-Z), the product group key (U,J,Z,R) of a six-digit serial number and a check digit calculated from all 10 characters and digits. The latter is used to exclude incorrect input by number turners.

Applying for the owner key for container identification

Each owner key is unique. This is ensured by registering with the International Bureau of Containers (BIC – Bureau International des Container – 14, Rue Jean Rey, 75015 Paris). Registration can be done directly with the BIC or can be carried out through a national organisation. The GERMAN representation of the BIC is the SGKV Studiengesellschaft für s/o in Frankfurt (www.sgkv.de).

Product group key in container label

The product group key consists of one of the three uppercase letters:

• U – for all containers
• J – for equipment that can be attached to the container
• Z – for trailers and chassis

The combination of owner key plus product group key is also known as “alpha prefix” or “owner code”.

The serial number in the container label

The registration number is unique and consists of six digits. If the container number consists of fewer than six digits, so many zeros are preceded until a six-digit sequence of numbers is obtained.

Calculating the check digit for container identification

The check digit is used to check the correct transmission of the owner code and registration number. This control is carried out automatically by data processing systems such as freight information systems (FIS) or transport information systems (TIS) and refuses to accept the container number if there is no compliance with the check digit.

The check digit according to ISO 6346

This is how the check procedure of the standardized container label works.

Test method for container number validation

The process is defined in such a way that multiple delivery errors cannot be overturned. This excludes the assumption of incorrect data. The test procedure works as follows:

Calculate check number: Step 1

Each letter of the alphabet is assigned an equivalent numerical value, which begins with 10 at the letter A and is counted further, with omission of the 11 and their multiples.

The digits of owner code and registration key are converted to these values.

Check number calculate step 2

The data processing system multiplies each digit according to its position by numerical values from 2 x 2 to 2 x 9 – see table below.

Check number calculate step 3

• Add all the results from step 2
• Divide them by 11
• Round all decimals to full numbers
• Multiply the full numbers by 11
• Subtract the result (4) from the addition result (1): This rest is the check digit!

If the rest is 10, the check digit is 0. Since check digit 0 can be duplicated, the standard recommends that you do not use registration numbers that result in the rest of 10.

If the check number is entered correctly, the system accepts the data – otherwise it would claim the entry.

Size and type codes for cargo containers

Overview of the size and type keys valid according to ISO 6346

Digit Length

Digit Height

ISO Type Codes

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