Container knowledge

In our information sheet Container Knowledge we clarify the most important questions for the coding of containers:

  • How is a container number composed?
  • How do I calculate a check number?
  • What are the encodings for container sizes?

Answers to these questions can be found here.

Container number according to ISO 6346

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

Structure of the container number

Container Knowledge 1

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 (

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

Container knowledge: Everything about ISO 6346

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

CodeLänge mmLänge ft
2605820 (TEU)
41219240 (FEU)
l1371645 (HC)

Digit Height

Width in mmHeight
2,438 (8ft)-2500over 2500MmFt
9Mind. 1219at least 4

ISO Type Codes

ISO CodeDescription
G0General – Openings at one or both ends
G1General – Passive vents at upper part of cargo space
G2General – Openings at one or both ends + full openings on one or both sides
G3General – Openings at one or both ends + partial openings on one or both sides
V0Fantainer – Non-mechanical, vents at lower and upper parts of cargo space
V2Fantainer – Mechanical ventilation system located internally
V4Fantainer – Mechanical ventilation system located externally
R0Integral Reefer – Mechanically refrigerated
R1Integral Reefer – Mechanically refrigerated and heated
R2Integral Reefer – Self-powered mechanically refrigerated
R3Integral Reefer – Self-powered mechanically refrigerated and heated
H0Refrigerated or heated or with removable equipment located externally; heat transfer coefficient K=0.4W/M2. K
H1Refrigerated or heated with removable equipment located internally
H2Refrigerated or heated or with removable equipment located externally; heat transfer coefficient K=0.7W/M2. K
H5Insulated – Heat transfer coefficient K=0.4W/M2. K
H6Insulated – Heat transfer coefficient K=0.7W/M2. K
U0Open Top – Openings at one or both ends
U1Open Top – Idem + removable top members in end frames
U2Open Top – Openings at one or both ends + openings at one or both sides
U3Open Top – Idem + removable top members in end frames
U4Open Top – Openings at one or both ends + partial on one and full at other side
U5Open Top – Complete, fixed side and end walls ( no doors )
T0Tank – Non dangerous liquids, minimum pressure 0.45 bar
T1Tank – Non dangerous liquids, minimum pressure 1.50 bar
T2Tank – Non dangerous liquids, minimum pressure 2.65 bar
T3Tank – Dangerous liquids, minimum pressure 1.50 bar
T4Tank – Dangerous liquids, minimum pressure 2.65 bar
T5Tank – Dangerous liquids, minimum pressure 4.00 bar
T6Tank – Dangerous liquids, minimum pressure 6.00 bar
T7Tank – Gas, minimum pressure 9.10 bar
T8Tank – Gas, minimum pressure 22.00 bar
T9Tank – Gas, minimum pressure to be decided
B0Bulk – Closed
B1Bulk – Airtight
B3Bulk – Horizontal discharge, test pressure 1.50 bar
B4Bulk – Horizontal discharge, test pressure 2.65 bar
B5Bulk – Tipping discharge, test pressure 1.50 bar
B6Bulk – Tipping discharge, test pressure 2.65 bar
P0Flat or Bolter – Plain platform
P1Flat or Bolter – Two complete and fixed ends
P2Flat or Bolter – Fixed posts, either free-standing or with removable top member
P3Flat or Bolter – Folding complete end structure
P4Flat or Bolter – Folding posts, either free-standing or with removable top member
P5Flat or Bolter – Open top, open ends (skeletal)
S0Livestock carrier
S1Automobile carrier
S2Live fish carrier
Information sheet Container Knowledge

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