Tool · ISO 6346
Container number check digit calculator
Paste a container number to check whether it is valid. bexy recomputes the ISO 6346 check digit, splits the number into owner code, category and serial, and shows every step of the calculation.
How a container number is built
A container number has eleven characters, defined by ISO 6346: a three-letter owner code registered with the BIC, a one-letter category identifier (U for freight containers, J for detachable equipment, Z for trailers and chassis), a six-digit serial number and a final check digit.
How the check digit is calculated
- Give each of the first ten characters a value: digits count as themselves, letters run from A = 10 upwards while skipping every multiple of 11.
- Multiply each value by 2 raised to its position, from 2⁰ = 1 for the first character to 2⁹ = 512 for the tenth.
- Add the ten products and divide by 11. The remainder is the check digit; a remainder of 10 becomes 0.
A = 10B = 12C = 13D = 14E = 15F = 16G = 17H = 18I = 19J = 20K = 21L = 23M = 24N = 25O = 26P = 27Q = 28R = 29S = 30T = 31U = 32V = 34W = 35X = 36Y = 37Z = 38
Worked example · CSQU3054383
| Character | Value | Weight | Product |
|---|---|---|---|
| C | 13 | 1 | 13 |
| S | 30 | 2 | 60 |
| Q | 28 | 4 | 112 |
| U | 32 | 8 | 256 |
| 3 | 3 | 16 | 48 |
| 0 | 0 | 32 | 0 |
| 5 | 5 | 64 | 320 |
| 4 | 4 | 128 | 512 |
| 3 | 3 | 256 | 768 |
| 8 | 8 | 512 | 4096 |
Sum 6185 · 6185 mod 11 = 3 · check digit 3 · valid
Frequently asked questions
- What is the format of a shipping container number?
- A container number has eleven characters: a three-letter owner code, a one-letter category identifier (U for a freight container), a six-digit serial number and a final check digit, for example CSQU 305438 3. The layout is defined by ISO 6346 and the owner codes are registered with the BIC, the Bureau International des Containers.
- How is the container check digit calculated?
- Each of the first ten characters gets a numeric value: digits count as themselves and letters run from A = 10 upwards, skipping every multiple of 11 (so K = 21, L = 23). Each value is multiplied by 2 raised to its position, starting at 2⁰ for the first character, the ten products are added, the total is divided by 11 and the remainder is the check digit. A remainder of 10 becomes 0.
- What does it mean if the check digit does not match?
- The number was almost certainly mistyped or misread: a swapped pair of digits, a 0 for an O, a 1 for an I. The check digit catches the vast majority of single-character errors. Re-read the number from the container door, the Bill of Lading or the booking confirmation and check again.
- Can I track a container by its number on bexy?
- Yes. Paste a valid container number into the search on bexy and it resolves to the shipment it travels under, with the vessel, ports, estimated arrival and the latest status of every container on that Bill of Lading — free, with no account.