What is the Container Check Digit?
The container check digit provides a means of validating the container number, based on the accuracy of the owner/operator code and serial number.
This allows any parties in the supply chain to automatically validate container numbers and easily identify incorrect container numbers in data entry.
Format of a Container Number
Generally, the number that identifies a container follows ISO rules and includes the prefix of the owner or builder, a letter for the type of equipment, the serial number and the check digit.
How to Calculate the Check Digit for a Shipping Container Number
The check digit is the last digit in a container number and ensures the validity of the sequence. Follow these steps:
Convert Letters to Numbers
Assign values to letters using this table:
| A | B | C | D | E | F | G | H | I | J | K | L | M |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 10 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 23 | 24 |
| N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 34 | 35 | 36 | 37 | 38 |
Multiply by Weight
For each character (excluding the check digit), multiply its numeric value by a positional weight with this pattern: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512.
Sum the Results
Add all the products from Step 2.
Calculate the Modulus
Divide the sum by 11 and take the remainder.
Determine the Check Digit
If the remainder is 10, the check digit is 0.
Otherwise, the check digit is the remainder.
Example
Container Number: CSQU3054383
Convert to Numbers: C = 13, S = 28, Q = 26, U = 31, 3 = 3, 0 = 0, 5 = 5, 4 = 4, 3 = 3, 8 = 8
Apply Weights: 13×1, 28×2, 26×4, 31×8, 3×16, 0×32, 5x64, 4×128, 3×256, 8×512
Result: 13 + 56 + 104 + 248 + 48 + 0 + 320 + 512 + 768 + 4096 = 5765
Calculate Modulus: 5765 mod 11 = 3
Check Digit: 3
Thus, the full container number is CSQU3054383.
