Free Tool

Container Number Checker

Paste any shipping container number to validate its ISO 6346 check digit, break down what each part means, and see which carrier the owner code belongs to. Runs in your browser — nothing is sent anywhere.

How the check digit works

Every container number carries its own error detection. That is what lets a checker like this one tell you a number is wrong before you book anything against it.

A container number is eleven characters, defined by ISO 6346: a three-letter owner code, a one-letter equipment category, a six-digit serial number, and a final check digit.

  1. Each of the first ten characters is converted to a number. Digits are themselves; letters run A=10 through Z=38, skipping every value that is a multiple of 11 — which is why there is no 11, 22 or 33 in the table.
  2. Each value is multiplied by 2 raised to the power of its position: the first character by 1, the second by 2, the third by 4, and so on up to 512.
  3. Those products are added together and divided by 11. The remainder is the check digit; a remainder of 10 is written as 0.

Because the weights differ for every position, swapping two characters almost always changes the result — which is exactly the mistake people make when copying a number off a bill of lading by hand.

What the parts mean

MAEUOwner code + categoryThree letters registered with the BIC, then U for a freight container (J for detachable equipment, Z for trailers and chassis).
342383Serial numberSix digits assigned by the owner. No meaning beyond being unique within that owner's fleet.
1Check digitCalculated from the ten characters before it. If it doesn't match, the number is wrong.

A valid number is not the same as a real one

Worth being clear about the limit: the check digit only proves a number is internally consistent. It cannot tell you the container exists, who is carrying it, or where it is. Any correctly-formed number passes — including one nobody ever built.

To answer where a box actually is, the number has to be tracked against carrier data. That is what Shyppy does: paste the number above and it goes straight into live tracking across ocean, air and courier, with alerts when the status or ETA changes.

Track by carrier

Container tracking for the major ocean lines:

Maersk

MAEU, MSKU, MRKU containers

MSC

MSCU, MEDU containers

CMA CGM

CMAU, CGMU containers

COSCO

COSU, CBHU containers

Hapag-Lloyd

HLXU, HLBU containers

Evergreen

EGLV, EMCU containers

ONE

ONEU, NYKU, MOLU containers

ZIM

ZIMU, ZCSU containers

Common questions

What is a container number check digit?

The 11th and final character. It is calculated from the ten before it under ISO 6346, so it catches most typing and transcription errors.

Why does my container number fail validation?

Usually a transposed pair of digits, or a zero read as the letter O. Occasionally the number was written without its check digit. If it came off a bill of lading and fails, check it against the physical container marking before booking against it.

Can I tell the carrier from the number?

Often — owner codes are registered, so MAEU is Maersk and MSCU is MSC. But many boxes are leased, in which case the code identifies the leasing company, not the line carrying it.

Does this work for air waybills and courier numbers?

Yes. The box above also recognises 11-digit IATA air waybills — including their modulo-7 check digit — and the formats used by UPS, FedEx, DHL and postal services.

Track it, don't just check it

Ocean, air and courier in one place, with alerts when something changes.

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