The Mystery of Container Numbers Solved

April 16, 2019

5 minute read

The Mystery of Container Numbers Solved

April 16, 2019

5 minute read

Like snowflakes, every international shipping container in the world has a unique identifier – its number.  No two are the same.

What do all those mysterious letters and numbers mean?   It’s a combination of a four-letter alpha prefix, followed by 6 numbers and a final “check digit.”

Four letter (ALPHA) prefix – the first three (3) characters represent the container’s owner. The forth is always “U” identifying it as a container “unit.” This is known as the BIC Code (

Six-digit (NUMERIC) suffix – this is created by the owner based on their own conventions.

Check Digit – a single check digit is added at the end and validates the container number throughout the ocean freight shipping world.

To calculate the check digit use these 3 foolproof steps…

Step 1 – a numerical value is assigned to each letter of the alphabet beginning with A=10, B=12, etc. Multiples of the number 11 are not used…that’s why B doesn’t equal 11 and V does not equal 22.  Find the numerical value for each of the 4 letters in your container number.

Step 2 – get out your calculator. Each numerical value for each of the container’s 10 positions is multiplied using this formula;

Position 1 X 1Position 6 X 32
Position 2 X 2Position 7 X 64
Position 3 X 4Position 8 X 128
Position 4 X 8Position 9 X 256
Position 5 X 16Position 10 X 512

Step 3 – Sum all results from step 2, then divide by 11 and round the result down to the lower whole number and multiply x 11

Subtract the resulting number from the sum of step 2 and you have your check digit!  That is the last number on the container.

Keeping track of containers by their number is important in the drayage industry to ensure the right container is delivered and to deter theft by scammers. If you are ever in doubt about whether a container number is real, use the formula above to see if the “check digit” is correct.  If not, you may be being scammed.

Protect yourself from scammers by using only carriers in the DrayMaster online quote system.  DrayMaster vets all carriers before allowing them to participate in the system thereby ensuring that your containers are moved by reputable carriers, not thieves pretending to be someone else.

See how DrayMaster can protect your livelihood, if you are a 3PL, Freight Forwarder or broker…register for our Demo Webinar. Truckers can schedule a demo here.

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