Container number format (ISO 6346)
Every intermodal shipping container carries a unique 11-character identification number defined by the ISO 6346 standard, for example CSQU3054383. Knowing how it is built helps you spot typos and see who owns a container.
Check a container number
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The four parts
- Owner code (3 letters, CSQ in the example): registered with the Bureau International des Containers (BIC).
- Equipment category identifier (1 letter): U for freight containers, J for detachable freight-container-related equipment, Z for trailers and chassis.
- Serial number (6 digits, 305438): chosen by the owner.
- Check digit (1 digit, 3): calculated from the first 10 characters, so most typing errors can be detected.
How the check digit is calculated
Each letter gets a value starting at A = 10 and skipping multiples of 11 (so B = 12, C = 13 … K = 21, L = 23 … U = 32, V = 34 … Z = 38); digits keep their value. Multiply the value of each of the first 10 characters by 2 to the power of its position (1, 2, 4, 8 … 512), add the results, divide by 11 and keep the remainder. A remainder of 10 gives a check digit of 0.
For CSQU305438: C 13×1 + S 30×2 + Q 28×4 + U 32×8 + 3×16 + 0×32 + 5×64 + 4×128 + 3×256 + 8×512 = 6185. 6185 divided by 11 leaves 3, so the full number is CSQU3054383.
Owner code and carrier
The owner code tells you who owns the container, not always who carries it. Carriers often have several owner codes, and many containers belong to leasing companies and are operated by whichever carrier leases them. The carrier pages list the codes each carrier uses, for example Maersk or COSCO; BerthTime uses them to suggest the carrier and lets you change it.
Size and type code
Next to the number, containers also show a 4-character size and type code from the same standard. The first character gives the length, the second the height and width, and the last two the type. For example, 22G1 is a 20-foot general-purpose container 8 ft 6 in high, and 45G1 is a 40-foot high-cube general-purpose container 9 ft 6 in high.
Once your number passes the check, you can track it: see How to track a container or start a free trial.