ISO 6346 is an international standard covering the coding, identification and marking of intermodal (shipping) containers used within containerized intermodal freight transport by the International Organization for Standardization (ISO). The standard establishes a visual identification system for every container that includes a unique serial number (with check digit), the owner, a country code, a size, type and equipment category as well as any operational marks. The register of container owners is managed by the International Container Bureau (BIC).

Identification system Example of an ISO 6346 compliant container number:

The illustrated example is a code for a container owned by Hapag-Lloyd AG.BIC Codes online, accessed 22 March 2018

Owner code The owner code consists of three capital letters of the Latin alphabet to indicate the owner or principal operator of the container. Such code needs to be registered at the Bureau International des Containers in Paris to ensure uniqueness worldwide. An owner can apply for more than one code, as normally the first 2 letters are used as the owner code and the third is used to indicate pool (e.g. HLA, HLB, HLX are some Hapag-Lloyd codes to indicate whether container is standard, reefer...)

Equipment category identifier The equipment category identifier consists of one of the following capital letters of the Latin alphabet: U for all freight containers J for detachable freight container-related equipment Z for trailers and chassis

Presently, all official BIC container codes end in "U". However, the Association of American Railroads recognizes similar codes for their containers and trailers travelling by rail in North America, though these are not recognized by the BIC and lack check digits.

Under the ISO code, then, only U, J, and Z are in use. The refrigerated (reefer) container is identified by means of the size type code.

Serial number The serial number consists of 6 numeric digits, assigned by the owner or operator, uniquely identifying the container within that owner/operator's fleet.

Check digit The check digit consists of one numeric digit providing a means of validating the recording and transmission accuracy of the owner code and serial number.

To compute the check digit, the letters have to be converted to numbers. This is done in three steps:

Calculation step 1 An equivalent numerical value is assigned to each letter of the alphabet, beginning with 10 for the letter A (11 and multiples thereof are omitted):

A B C D E F G H I J K L M 10 12 13 14 15 16 17 18 19 20 21 23 24

N O P Q R S T U V W X Y Z 25 26 27 28 29 30 31 32 34 35 36 37 38

The individual digits of the serial number keep their numeric value.

Calculation step 2 Each of the numbers calculated in step 1 is multiplied by 2position, where position is the exponent to base 2. Position starts at 0, from left to right.

The following table shows the multiplication factors: 1. nbr 2. nbr 3. nbr 4. nbr 5. nbr 6. nbr 7. nbr 8. nbr 9. nbr 10. nbr 20 21 22 23 24 25 26 27 28 29 1 2 4 8 16 32 64 128 256 512

Calculation step 3

If the final difference is 10, then the check digit becomes 0. To ensure that this does not happen the standard recommends that serial numbers should not be used which produce a final difference of 10; however, there are containers in the market which do not follow this recommendation, so handling this case has to be included if a check digit calculator is programmed.

Virtually all programming languages have a modulo operator for step 3; some languages (also) return the decimal portion which must be multiplied by 11 to get a proper modulo. 11 is used as divisor because a container number has 11 letters and digits in total. In step 1 the numbers 11, 22 and 33 are left out as they are multiples of the divisor.

Example

C S Q U 3 0 5 4 3 8 Calc. 13 30 28 32 3 0 5 4 3 8 × 1 2 4 8 16 32 64 128 256 512 13 60 112 256 48 0 320 512 768 4096 6185 [a] b) Division by 11: 562.272... c) Erase decimal digits: 562 d) Multiply by 11: 6182 a) minus d) = Check Digit: 3

Practical problems In day-to-day business it happens that containers do appear which do not follow the ISO 6346 identification at all; however, they are fully CSC safety approved containers. Usually these are "shippers owned" containers (SOC), which means that they are not owned by the carrier but supplied by the cargo owners (shippers). They may have no registered owner code and no category identifier and have no check digit. It is advisable to follow ISO 6346 as the absence of a compliant identification code causes problems for both carriers and container terminals to correctly identify the equipment and properly deliver the cargo, because computer systems require ISO 6346-conforming naming and as such missing prefixes are invented. For example, YYYY at the carrier and XXXX at the terminal causes the equipment to mismatch. Moreover, since ISO 6346 identification has become a requirement in international Customs conventions (Customs Conventions on Containers and Istanbul Convention), many Customs Administrations have begun validating that containers are marked as per the standard.

Size and type codes The codes are compiled of the following elements: First character, representing the length (coded) Second character, representing the width and height (coded) Third and fourth character indicating the type of the container

The following is an overview of the most common codes:

ISO Type Group ISO Size Type Code Description Code Description 20GP GENERAL PURPOSE CONT. 20G0 GENERAL PURPOSE CONT. 20G1 GENERAL PURPOSE CONT. 20HR ISOLADO CONTAINE REEFER 20H0 INSULATED CONTAINER 20PF FLAT (FIXED ENDS) 20P1 FLAT (FIXED ENDS) 20TD TANK CONTAINER 20T3 TANK CONTAINER 20T4 TANK CONTAINER 20T5 TANK CONTAINER 20T6 TANK CONTAINER 20TG TANK CONTAINER 20T7 TANK CONTAINER 20T8 TANK CONTAINER 20TN TANK CONTAINER 20T0 TANK CONTAINER 20T1 TANK CONTAINER 20T2 TANK CONTAINER 22BU BULK CONTAINER 22B0 BULK CONTAINER 22GP GENERAL PURPOSE CONT. 22G0 GENERAL PURPOSE CONT. 22G1 GENERAL PURPOSE CONT. 22HR INSULATED CONTAINER 22H0 INSULATED CONTAINER 22PC FLAT (COLLAPSIBLE) 22P3 FLAT (COLLAPSIBLE) 22P8 FLAT (COLL.FLUSH FOLDING) 22P9 FLAT (COLLAPSIBLE) 22PF FLAT (FIXED ENDS) 22P1 FLAT (FIXED ENDS) 22P7 FLAT (GENSET CARRIER) 22RC REEFER CONT.(NO FOOD) 22R9 REEFER CONT.(NO FOOD) 22RS BUILT-IN GEN. F. POWER SPLY OF REEF 22R7 BUILT-IN GEN. F. POWER SPLY OF REEF 22RT REEFER CONTAINER 22R1 REEFER CONTAINER 22SN NAMED CARGO CONTAINER 22S1 NAMED CARGO CONTAINER 22TD TANK CONTAINER 22T3 TANK CONTAINER 22T4 TANK CONTAINER 22T5 TANK CONTAINER 22T6 TANK CONTAINER 22TG TANK CONTAINER 22T7 TANK CONTAINER 22T8 TANK CONTAINER 22TN TANK CONTAINER 22T0 TANK CONTAINER 22T1 TANK CONTAINER 22T2 TANK CONTAINER 22UP HARDTOP CONTAINER 22U6 HARDTOP CONTAINER 22UT OPEN TOP CONTAINER 22U1 OPEN TOP CONTAINER 22VH VENTILATED CONTAINER 22V0 VENTILATED CONTAINER 22V2 VENTILATED CONTAINER 22V3 VENTILATED CONTAINER 25GP GP-CONTAINER HIGH CUBE 25G0 GP-CONTAINER HIGH CUBE 26GP GP-CONTAINER SUPER HIGH CUBE 26G0 GP-CONTAINER SUPER HIGH CUBE 26HR INSULATED CONTAINER 26H0 INSULATED CONTAINER 28TG TANK FOR GAS 28T8 TANK FOR GAS 28UT OPEN TOP (HALF HEIGHT) 28U1 OPEN TOP (HALF HEIGHT) 28VH VE-HALF-HEIGHT =1448 MM HEIGHT 28V0 VE-HALF-HEIGHT =1448 MM HEIGHT 29PL PLATFORM 29P0 PLATFORM 2EGP GEN. PURP. WITHOUT VENT WIDTH 2.5M 2EG0 HIGH CUBE CONT. (WIDTH 2.5M) 42GP GENERAL PURPOSE CONT. 42G0 GENERAL PURPOSE CONT. 42G1 GENERAL PURPOSE CONT. 42HR INSULATED CONTAINER 42H0 INSULATED CONTAINER 42PC FLAT (COLLAPSIBLE) 42P3 FLAT (COLLAPSIBLE) 42P8 FLAT (COLL.FLUSH FOLDING) 42P9 FLAT (COLLAPSIBLE) 42PF FLAT (FIXED ENDS) 42P1 FLAT (FIXED ENDS) 42PS FLAT (SPACE SAVER) 42P6 FLAT SPACE SAVER 42RC REEFER CONT.(NO FOOD) 42R9 REEFER CONT.(NO FOOD) 42RS REEFER CONT.(DIESEL GEN.) 42R3 REEFER CONT.(DIESEL GEN.) 42RT REEFER CONTAINER 42R1 REEFER CONTAINER 42SN NAMED CARGO CONTAINER 42S1 NAMED CARGO CONTAINER 42TD TANK CONTAINER 42T5 TANK CONTAINER 42T6 TANK CONTAINER 42TG TANK CONTAINER 42T8 TANK CONTAINER 42TN TANK CONTAINER 42T2 TANK CONTAINER 42UP HARDTOP CONTAINER 42U6 HARDTOP CONTAINER 42UT OPEN TOP CONTAINER 42U1 OPEN TOP CONTAINER 45BK BULK CONTAINER 45B3 BULK CONTAINER 45GP HIGH CUBE CONT. 45G0 HIGH CUBE CONT. 45G1 HIGH CUBE CONT. 45PC FLAT (COLLAPSIBLE) 45P3 FLAT (COLLAPSIBLE) 45P8 FLAT (COLL.FLUSH FOLDING) 45RC REEFER CONT.(NO FOOD) 45R9 REEFER CONT.(NO FOOD) 45RT REEFER HIGHCUBE CONTAINER 45R1 REEFER HIGHCUBE CONTAINER 45UT OPEN TOP CONTAINER 45U1 OPEN TOP CONTAINER 45UP HIGH CUBE HARDTOP CONT. 45U6 HIGH CUBE HARDTOP CONT. 46HR INSULATED CONTAINER 46H0 INSULATED CONTAINER 48TG TANK FOR GAS 48T8 TANK FOR GAS 49PL PLATFORM 49P0 PLATFORM 4CGP GP CONTAINER 4CG0 GP CONTAINER (WIDTH 2.5 M) L0GP LOW CUBE CONT. L0G1 LOW CUBE CONT. L2GP STANDARD CONT. L2G1 STANDARD CONT. L5GP HIGH CUBE CONT. L5G1 HIGH CUBE CONT.

Use the below to calculate size/type of a less commonly used ISO 6346 containers:

ISO Length Codes Second size code character Code Container length Code Container height Width 1 0 1 2 2 2 3 4 4 5 55 B 6 > C 8 G 9 <= H C < x ≤ L (1995 edition, replaced by 5 in the 2022 edition) D M E N F >