Decoding the Container Number (What Do Those 11 Characters Mean?)

You type it into TraceContainer.com to find your cargo: MSKU1234567.

But have you ever stopped to wonder what that code actually means? It looks like a random string of letters and numbers, but it is actually a sophisticated ID system governed by international law (ISO 6346).

Every character tells a story about who owns the box, what it is made of, and if it is fake. Here is how to crack the code.

Decoding Your Container Number: What Do the 11 Characters Mean? 

The Formula: 4 Letters + 7 Numbers

Every standard container number has exactly 11 characters. We can break them down into four distinct parts.

Let's use the example: MSKU 123456 7

Part 1: The Owner Code (First 3 Letters)

• Example: MSK

• Meaning: This tells you who owns the container.

  • MSK = Maersk

  • MSC = Mediterranean Shipping Company

  • HLC = Hapag-Lloyd

  • TRI = Triton (Leasing Company)

These codes are not random. They must be registered with the BIC (Bureau International des Containers) in Paris. If a container has a code that isn't registered, it is likely a fake or "shipper-owned" box that can't be used for international transport.

Part 2: The Category Identifier (4th Letter)

• Example: U

• Meaning: This single letter tells you what kind of equipment it is.

  • U = Freight Container (Standard shipping container).

  • J = Detachable Equipment (Like a generator).

  • Z = Trailer or Chassis.

  • R = Refrigerated (Rarely used in the ID itself, usually just 'U' is used for all containers).

99% of the time, this letter will be "U".

Part 3: The Serial Number (Next 6 Digits)

• Example: 123456

• Meaning: This is simply the unique ID number assigned by the owner. It’s just like the license plate on a car. If the number is short (e.g., "55"), they add zeros to the front to make it 6 digits (e.g., "000055").

Part 4: The Check Digit (The Magic 7th Number)

• Example: 7

• Meaning: This is the most interesting part. The very last number (often inside a square box on the container door) is the Check Digit.

It is calculated using a complex mathematical algorithm based on the previous 10 letters and numbers.

• Why does it exist? To prevent typos.

• How it works: When a port worker types the container number into a computer, the computer instantly runs the math formula. If the calculated digit doesn't match the last number typed, the computer screams "ERROR!"

• The Result: This stops a typo (like typing "123546" instead of "123456") from sending your container to the wrong country.

Bonus Code: The "ISO Size Type" (22G1, 45R1)

Below the long ID number, you will often see a 4-character code. This tells you the Size and Type.

• First Character (Length):

  • 2 = 20ft

  • 4 = 40ft

  • L = 45ft

• Second Character (Height):

  • 2 = Standard Height (8'6")

  • 5 = High Cube (9'6")

• Last Two Characters (Type):

  • G1 = General Purpose (Dry)

  • R1 = Reefer (Frozen)

  • T1 = Tank

  • P1 = Flat Rack / Platform

Examples:

• 22G1 = 20ft Standard Dry

• 45G1 = 40ft High Cube Dry

• 45R1 = 40ft High Cube Reefer

Summary

The next time you are behind a truck on the highway, look at the container.

• See a code starting with MSKU? You know it belongs to Maersk.

• See 45G1? You know it's a 40ft High Cube.

• See the boxed number at the end? You know that's the math wizard keeping the data safe.

At TraceContainer.com, our algorithm validates that "Check Digit" instantly, ensuring you never track a ghost container.