How to cite this reference
Terminal49. ISO 6346 check-digit calculation reference. Updated August 17, 2026. https://terminal49.com/tools/container-check-digit-calculatorContainer check digit calculator
Paste the first 10 characters to calculate the final digit, or enter a complete 11-character container number to check it against ISO 6346. No signup required.
ISO 6346 check-digit calculator
Enter the first 10 characters to calculate the final digit, or check a complete 11-character container number.
What the 11 characters mean
- 1. Owner code: the first three letters identify the registered owner or principal operator.
- 2. Equipment category: the fourth letter is U, J, or Z.
- 3. Serial number: six digits assigned by the owner or operator.
- 4. Check digit: the final digit validates the recording of the first 10 characters.
How ISO 6346 calculates the digit
Each letter receives a numeric value that skips multiples of 11. The calculator multiplies each of the first 10 character values by a power of two based on its position, adds the results, and takes the remainder after division by 11. A remainder of 10 is written as 0.
Need to identify the company associated with a code instead? Use the free SCAC and ocean carrier lookup.
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Download, cite, or embed the check-digit calculator
Download the letter values and position weights used by this calculator. Updated August 17, 2026. No signup or access key required.
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<iframe src="https://terminal49.com/tools/embed/container-check-digit-calculator" title="ISO 6346 container check digit calculator" width="100%" height="520" loading="lazy"></iframe>Container check digit questions
What is a container check digit?
It is the final digit of an ISO 6346 container number. Systems calculate it from the owner code, equipment category, and six-digit serial number to catch common recording errors.
Can I calculate a missing check digit?
Yes. Enter the first 10 characters: three owner-code letters, one equipment category letter, and six serial digits. The calculator returns the 11th character.
Does a valid check digit prove that the container exists?
No. It only proves that the characters are mathematically consistent. It does not confirm that the owner code is currently registered, that the container is active, or that a specific carrier is moving it.
What do U, J, and Z mean in a container number?
The fourth character is the equipment category identifier. U is used for freight containers, J for detachable container-related equipment, and Z for trailers and chassis.
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