A container is a reusable transport equipment designed for container freight shipping to the point of destination by means of road, rail, and water transport.

A container can be reused if its loading and installation have been done correctly. Misuse can lead to it going out of service and damage of the goods. To prevent such situations from happening, every container is given a marking.

The current standard which deals with the coding, identification, and marking of containers is ISO 6346, dated 1996. The standards for international shipping containers are managed by the International Container Bureau (BIC).

A distinction is drawn between compulsory and optional marks. Optional marks can be assigned at the will of the owner for easy recognition of goods.

Compulsory marking must be used on all containers and is applied onto the door and other planes of the container (sidewalls, roof, bottom).

The container identification number consists of the:

  • owner code, consisting of three capital letters;
  • equipment category identifier — one of the capital letters – U, J, or Z;
  • serial number of six numeric digits;
  • check digit of one numeric digit.

The owner code must be unique and registered with the BIC (either directly or through a national representative of the organization).

The letter in the equipment category identifier stands for:

U - freight containers;
J - detachable freight container-related equipment;
Z - trailers and chassis.

The owner code and equipment category identifier can be grouped under one term, also known as an alpha prefix.

container marking

If the owner code is absent, the container cannot be identified.

The registration or serial number consists of six digits. If the number has fewer than six digits, zeros are added in the beginning of the number to make a six-digit number sequence.

The last digit in the container number – the check digit – is always a single-digit number. It is usually placed in a box to single it out from the rest of the numbers in the registration code.

The check digit is used to verify the accuracy of the owner code, the equipment category identifier, and the registration number. If the result number of the automatic checking procedure does not correspond to the number in the check digit – no transport or freight information system will be able to process the container.

The procedure has been introduced to ensure the correctness of input data of the international container shipping information systems.

The checking procedure is as follows: every letter is assigned an equivalent numerical value on the basis of its position in the alphabet, beginning with 10 for the Latin letter A (11 and its multipliers are omitted). The individual digits of the registration number keep their numeric value). Every number is multiplied by 2exponent, where the value of the exponent corresponds to the position of the digit in the registration number from 0 to 9, left to right (the first digit is multiplied by 1, the second – by 2, the third – by 4, the fourth – by 8, the fifth – by 16, the sixth – by 32, the seventh – by 64, the eighth – by 64, the ninth – by 256, and the tenth – by 512). The results are summed up, after that, divided by 11, and rounded down to zero (made a whole number). The whole number is multiplied by 11. The result is subtracted from the result of the initial calculations (summation). The final difference is the check digit.

If the final number is 10, the check digit becomes 0. The standard doesn’t recommend the use of serial numbers which produce a final difference of 10.

Containers also have a sized and type code.The latter includes four elements:

  • the first character represents the length (2 for 20’’, 4 for 40’’, 3 for 30’’, for specific sizes a letter code is used);
  • the second character represents the width and the height;
  • the third and the fourth character indicate the type of the container.

The code for the length of the container is shown in the following table:

Character   Container length
mm ft
1 2,991 10
2 6,058 20
3 9,125 30
4 12,192 40
5-9 Spare
A 7,15  
B 7,315 24
C 7,43  
D 7,45 24,6
E 7,82  
F 8,1  
G 12,5 41
H 13,106 43
K 13,6  
L 13,716 45
M 14,63 48
N 14,935 49
P 16,154  

The code for the height and width of the container:

Width,m Character Container height Character for container width
mm ft > 2,438 m and <2,5 m > 2,5 m
2,438 0 2,438  8    
2,438  2,591  8’6  C
2,438  2,743  9  D
2,438  2,895 9’6  E
2,438  >2,895 >9’6   F
2,438   1,295 4’3     
2,438  <1,219 <4     

As the last two characters a group code can be used if the subgroup is not specified by the standard. The codes of container types are presented in the table.

General Code Group Code Type Type Code Characteristics









Unventilated general purpose container

G0 Openings at both ends
G1 Vents in upper part of cargo space
G2 Openings at one or both ends + full openings on one or both sides
G3 Openings at one or both ends + partial openings on one or both sides
G4-G9 Spare












General purpose container with ventilation

V0 Non-mechanical ventilation at the lower and upper parts of the cargo space
V1 Spare
V2 Mechanical ventilation installed in the container
V3 Spare
V4 Mechanical ventilation installed outside the container
V5-V9 Spare














Dry bulk containers, non-pressure resistant

B0 Closed
B1 Airtight
B2 Spare



Container for dry bulk cargo pressure control

B3 Horizontal discharge, test pressure 150kPa
B4 Horizontal discharge, test pressure 265kPa
B5 Tipping discharge, test pressure 150kPa
B6 Tipping discharge, test pressure 265kPa
  B7-B9 Spare









Named cargo containers

S0 Livestock container
S1 Automobile container
S2 Living fish container
S3-S9 Spare








Thermal containers (refrigerated, refrigerated and heated, self/externally powered)

R0 Mechanically refrigerated
RT R1 Mechanically refrigerated and heated
RS R2 Mechanically refrigerated, self-powered
  R3 Mechanically refrigerated and heated, self-powered
R4-R9 Undefined













Thermal container (refrigerated and/or heated with removable equipment)

H0 Refrigerated or heated with removable equipment located externally; heat transfer coefficient 0.4W/(m2*K)
H1 Refrigerated or heated with removable equipment located internally
H2 Refrigerated or heated with removable equipment located externally; heat transfer coefficient 0.7W/(m2*K)
H3-H4 Spare



H5 Insulated, heat transfer coefficient 0,4W/(m2*К)
H6 Insulated, heat transfer coefficient 0,7W/(м2*К)
H7-H9 Spare















Open-top container

U0 Openings at one or both ends
U1 Openings at one or both ends, removable roof
U2 Openings at one or both ends + openings on one or both sides
U3 Openings at one or both ends + openings on one or both sides + removable top members
U4 Openings at one or both ends + openings on one or both sides + full openings on one side
U5 Solid side and end walls (no doors)
U6-U9 Spare











Platform-container (with incomplete superstructure, removable walls, open and closed)

P0 Plain platform



P1 Platform with two complete, fixed end walls
P2 Platform with fixed posts and with removable top members



P3 Platform with folding complete end walls
P4 Platform with folding posts and with removable top members
PS P5 Platform open at the top and ends
  P6-P9  Spare









Tank container for non-dangerous liquids

T0 Minimum pressure 45 kPa
T1 Minimum pressure 150 kPa
T2 Minimum pressure 265 kPa



Tank container for dangerous liquids

T3 Minimum pressure 150 kPa
T4 Minimum pressure 265 kPa
T5 Minimum pressure 400 kPa
T6 Minimum pressure 600 kPa


Tank container for gasses

T7 Minimum pressure 910 kPa
T8 Minimum pressure 2200 kPa
T9 Minimum pressure to be assigned
 A  AS Air/surface container A0   

Optional mark includes country code, weight of the container, a symbol to denote containers for air freight transportation, a sign warning of overhead electrical danger, height of the container (for containers higher than 2.6m).

The country code consists of two capital letters of the Latin alphabet as stated in ISO 3166. The country implies the country of container registration, not the country of the owner or the shipping company that carries out the international transportations.

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