Container number and check digit
Also known as: Container prefix · Owner code · BIC code · ISO 6346 · Check digit
Every container has a unique number under the ISO 6346 standard, such as CSQU 305438 3: a 4-letter prefix, a 6-digit serial number, and one check digit.
In plain words
The first three letters are the owner code, registered with the BIC (Bureau International des Containers). The fourth letter is the equipment category: U for freight containers, J for detachable equipment such as gensets, and Z for trailers and chassis. Then come six serial digits and a final check digit, often shown in a box. Next to the number you usually see the ISO size-type code, for example 22G1 or 45G1.
The check digit catches typing mistakes. Each letter gets a value (A = 10, B = 12, C = 13, and so on, skipping 11, 22, and 33), and digits keep their value. Each of the first ten characters is multiplied by 2 to the power of its position (1, 2, 4, … 512). Add the results, divide by 11, and the remainder is the check digit (a remainder of 10 counts as 0). Always check the full number on the Bill of Lading, VGM, and customs papers — one wrong digit can stop the container.
Example from real shipping
For CSQU 305438: C = 13, S = 30, Q = 28, U = 32. The sum is 13×1 + 30×2 + 28×4 + 32×8 + 3×16 + 0×32 + 5×64 + 4×128 + 3×256 + 8×512 = 6,185. 6,185 ÷ 11 leaves a remainder of 3, so the full number is CSQU 305438 3. If a document says CSQU 305483 3, the check digit does not match, and you know there is a typing error.
Related terms
- CSCThe CSC plate is a metal plate on the container door that shows the container is approved as safe under the International Convention for Safe Containers (CSC, 1972).
- B/LA Bill of Lading (B/L) is the main document for sea freight. The carrier issues it when it takes the goods. It shows who can collect the goods at the destination.
- Container typesA side-by-side comparison of the common shipping container types: sizes, weights, capacity, pallet places, and typical cargo.
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