What is a Container Number? (BIC / ISO 6346 Explained)

A container number is a unique 11-character alphanumeric code assigned to every intermodal shipping container worldwide. It's printed on the container's exterior, encoded in the container's CSC plate, and used by every shipping line, port, customs authority, and tracking system to identify that specific unit.

The structure: 4 letters + 7 digits

Following the ISO 6346 international standard, a container number is composed of:

• Owner code: 3 capital letters (A-Z) identifying the container's owner or operator
• Category identifier: 1 capital letter — U for freight containers, J for detachable freight container-related equipment, Z for trailers and chassis
• Serial number: 6 digits, assigned sequentially by the owner
• Check digit: 1 digit, calculated from all preceding characters using a mod-11 algorithm

Common owner codes you'll see

• MSCU — MSC (Mediterranean Shipping Company)
• COSU — COSCO Shipping Lines
• CMAU — CMA CGM
• ONEU — Ocean Network Express
• HDMU — HMM
• NYKU, MOLU, KKTU — older NYK / MOL / K Line containers (now under ONE)
• TEMU — Textainer (one of the world's largest container lessors)

How the check digit is calculated

The check digit validates that the container number has not been transcribed incorrectly. Each of the first 10 characters is mapped to a numeric value (A=10, B=12, ..., Z=38 — skipping multiples of 11), then multiplied by a position weight (2^0, 2^1, ... 2^9). The sum is divided by 11; the remainder is the check digit (with 10 represented as 0).

MSCU 123456 7
↑↑↑↑ ↑↑↑↑↑↑ ↑
Owner  Serial  Check

How MariMetric uses the container number

When you enter a container number on MariMetric, the first 4 characters (the owner code) are used to detect which carrier issued the container. MariMetric then routes the request to the corresponding carrier adapter to retrieve real-time tracking data — all in under a second.