Shipping Container Number Validator

Every freight container that crosses the world has a code painted on its side: four letters, six digits and one more digit in a box. This is the container identifier defined in ISO 6346, and it is the key to bookings, bills of lading, customs declarations, port gate records and tracking. A transposed digit turns into a different container or none at all, which is why the last digit is a check digit. This validator performs the calculation and breaks a number into its parts.

The four elements

The first three letters are the owner code, registered with the Bureau International des Containers (BIC) and unique to a company. The fourth letter is the equipment category: U for a freight container, J for detachable freight-container-related equipment, Z for a trailer or chassis and R for a reefer. Next come six digits, the serial number chosen by the owner. The last digit is the check digit. Elsewhere on the box, the size and type code such as 22G1 tells the length, height and kind; it is not part of the ID and this page does not check it.

How the check digit is computed

Every character of the first ten is given a value. Digits keep their own value. Letters are numbered from A=10 in order but skip the multiples of 11 (11, 22, 33), so B=12, C=13 and so on up to Z=38. Each value is multiplied by 2 raised to the power of its position, counting from 0 for the first character, and the products are added. The sum is divided by 11, and the remainder is the check digit. If the remainder is 10, it is written as 0. Multiples of 11 are skipped because they would add nothing to a remainder modulo 11. For CSQU305438 the weighted sum is 6,185, and 6,185 leaves a remainder of 3 when divided by 11.

A worked example

Press Sample to check four numbers. CSQU3054383 is valid: owner code CSQ, category U (freight container), serial number 305438, check digit 3. The same container written as CSQU 305438-3, with spaces and a hyphen as it appears on paper, is also accepted. CSQU3054384 has the last digit changed, and the page reports that the check digit is wrong and that 3 is correct. ABC123 is rejected, with a message that explains what is expected: three owner letters, a category letter U, J, Z or R, six serial digits and one check digit, for example CSQU3054383. In the calculator below, entering CSQU305438 returns the check digit 3 and the complete number CSQU3054383.

Where mistakes come from

Hand-written and voice-relayed numbers are the usual source: confusing 0 with O, 1 with I, or reading 6 for 8. A spreadsheet can also strip spaces or convert a number to a date. Pasting a list of containers from a booking into this validator before submitting a shipping instruction catches the wrong ones in a second.

Limits

A valid number is consistent, but it does not prove that the container exists or belongs to a given shipping line. The page has no owner register and no tracking. Use the carrier’s website, the BIC code register or a tracking service for that. The calculation runs in your browser.

Related tools

• VIN Decoder and Validator checks another transport identifier.
• GTIN, EAN and UPC Check Digit Calculator covers pallet SSCC labels and products.
• Luhn Validator is the common check for cards.
• IBAN Validator is used for the payment side of a shipment.