VIN Check Digit Calculator

The Mathematics of the Modulo-11 VIN Check Digit

Unlike simple parity bits or CRC algorithms used in data networking, the automotive VIN check digit utilizes a specialized transliteration table coupled with position-dependent weighting. This design guarantees the detection of single-character transcription errors and the transposition of adjacent characters (such as typing "12" instead of "21").

Official Transliteration Key Table

Because computers and clerical staff process alphanumeric characters, the regulation translates each English letter into an equivalent numerical value:

Why Position Weights Prevent Transposition Errors

If every position had the same weight, switching two adjacent characters (e.g., swapping character 4 and 5) would yield the exact same sum, making transposition undetected. By giving position 4 a weight of 5 and position 5 a weight of 4, swapped digits produce a different sum and a mismatched modulo-11 remainder.