How Does a Shipping Container Get Its Number?

Have you ever looked at a shipping container and wondered what all those letters and numbers actually mean?

Every standard intermodal freight container has its own identification number. This number allows shipping lines, freight forwarders, ports, terminals, customs authorities and transport operators to identify the container as it moves through the global supply chain.

The system is internationally standardised under ISO 6346, so a container can be identified wherever it is in the world.

So, how does it work?

A standard container identification number consists of four letters followed by seven numbers.

For example:

MSCU 123456 7

The first three letters are the owner code. This identifies the registered owner or principal operator of the container. It doesn't necessarily mean the container belongs to a shipping line, containers can also be owned or operated by leasing companies and other equipment owners.

The fourth letter is the equipment category identifier. For a standard freight container, this is usually U. Other identifiers are used for equipment such as detachable freight container-related equipment and trailers or chassis.

The next six numbers are the serial number. This is assigned by the owner or operator and uniquely identifies that particular container within their fleet.

And then we have the final number, the check digit.

The check digit is calculated using a mathematical formula based on the letters and numbers in the container identification number. Its purpose is to help verify that the container number has been entered or transmitted correctly.

So, if a container number is entered incorrectly into a booking, terminal or transport system, the check digit can help identify a potential error.

But the container number isn't the only code you'll see on a shipping container.

Containers also carry a separate four-character size and type code. This provides information about the container's dimensions and type, for example, whether it is a 20’ container, 40’ container, high cube, refrigerated container or another specialised type.

All of this information is important because a container can pass through many different hands during its journey.

It might be collected from a factory, transported by truck to a port, loaded onto a vessel, discharged at its destination, moved through a container terminal and eventually delivered to a warehouse.

The container number provides a consistent way for all the different parties involved to identify that particular piece of equipment.

It appears across booking systems, bills of lading, terminal systems, customs documentation, transport instructions and tracking systems.

So, the next time you're standing beside a shipping container, take a look at the numbers on the side.

They might look like a random combination of letters and numbers, but they are actually part of a globally standardised container identification system that helps keep international freight moving.

Four letters. Seven numbers. One container.

It's a small piece of information that plays a very big role in global logistics.

Source: ISO 6346 and the Bureau International des Containers (BIC).