The check digit is the eleventh character of a container number, computed from the first ten under ISO 6346. Letters map to numeric values, each position is weighted by a power of two, and the sum modulo 11 gives the digit, with a result of ten recorded as zero.
Its job is catching transcription errors before they propagate: a mistyped letter or transposed digits almost always breaks the checksum, so booking systems, terminal gates, and tracking tools can reject a bad number instantly instead of creating a phantom container.
The letter mapping starts at A = 10 and skips multiples of eleven (11, 22, 33), which is why the sequence jumps. Because the arithmetic is fixed by the standard, any system can validate a container number offline with no registry lookup.
A tracking request that returns nothing at all, rather than an early empty timeline, is often just a bad number. Running the digits through the TrackingMCP container checker takes seconds and tells you whether to fix the reference or investigate the shipment. Valid numbers then go straight into tracking.
The check digit is the eleventh character of a container number, computed from the first ten under ISO 6346. Letters map to numeric values, each position is weighted by a power of two, and the sum modulo 11 gives the digit, with a result of ten recorded as zero.
No. It proves the number is well formed. A syntactically valid number can still belong to no active box; existence is confirmed by the carrier’s or terminal’s systems responding with events.
The ISO 6346 calculation can yield ten, and the standard records it as zero. Some owners avoid issuing serials whose checksum is ten to prevent ambiguity, but numbers ending in a mapped zero remain valid.
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