One element that is fairly consistent in VIN numbers is the use of position 9 as a **Check digit**, compulsory for vehicles in North America and used fairly consistently even outside this rule.

If trying to validate a VIN with a check digit, first either: (a) remove the check digit for the purpose of calculation; or (b) utilize the multiplicative property of zero in the weight to cancel it out. You should later compare the old value of the check-bit, with the new to ensure the VIN's validity.

## Overview of the processEdit

An overview of the process for calculating a VIN's check digit is as follows:

- Remove all of the letters from the VIN by transliterating them with their numeric counterparts. Numerical counterparts can be found in the table below.
- Multiply this new number, the yield of the transliteration, with the assigned weight. Weights can be found in the table below.
- Sum the resulting products.
- Modulus the sum of the products by 11, to find the remainder.
- If the remainder is
*10*replace it with*X*.

## Transliterating the numbersEdit

Transliteration consists of removing all of letters and substituting them with their appropriate numerical counterparts. These numerical alternatives can be found in the following chart. *I*, *O* and *Q* are not allowed, and can not exist in a valid VIN; for the purpose of this chart, they have been filled in with *N/A* (not applicable). Numerical digits use their own values.

A: 1 |
B: 2 |
C: 3 |
D: 4 |
E: 5 |
F: 6 |
G: 7 |
H: 8 |
N/A |

J: 1 |
K: 2 |
L: 3 |
M: 4 |
N: 5 |
N/A | P: 7 |
N/A | R: 9 |

S: 2 |
T: 3 |
U: 4 |
V: 5 |
W: 6 |
X: 7 |
Y: 8 |
Z: 9 |

*S* is 2, and not 1. There is no left-alignment linearity.

## Weights used in calculationEdit

The following is the weight factor for each position in the VIN. The 9th position is that of the check digit. It has been substituted with a 0, which will cancel it out in the multiplication step.

Position | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Weight | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 10 | 0 |
9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 |

## Worked exampleEdit

Consider the hypothetical VIN 1M8GDM9A_KP042788, where the underscore will be the check digit.

VIN | 1 | M | 0 | H | A | 0 | 9 | 2 | N/A | C | 6 | 8 | 2 | 2 | 1 | 9 | 6 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Value | 1 | 4 | 8 | 7 | 4 | 4 | 9 | 1 | 0 | 2 | 7 | 0 | 4 | 2 | 7 | 8 | 8 |

Weight | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 10 | 0 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 |

Products | 8 | 28 | 48 | 35 | 16 | 12 | 18 | 10 | 0 | 18 | 56 | 0 | 24 | 10 | 28 | 24 | 16 |

- The VIN's Value is calculated from the above table, this number will be used in the rest of the calculation.
- Copy over the
*weights*from the above table. - The
*products*row is a result of the multiplication of the vertical columns:*Value*and*Weight.* - The products (8,28,48,35..24,16) are all added together to yield a sum of
*351* - One of the following operations:
- 351 % 11 = 10 (where % is a modulo operator)
- 351 ÷ 11 = 31 10/11
- 351 ÷ 11 = 31.9090-

- The check digit is 10, so it has been transliterated into
*X*.

With a check digit of 'X' the VIN: `1M8GDM9A ?KP042788` is written with the check bit as:

`1M8GDM9A`.

*X*KP042788*Straight-ones* (seventeen consecutive '1's) will suffice the check-digit. This is because a value of one, multiplied against 89 (sum of weights), is still 89. And 89 % 11 is 1, the check digit. This is an easy way to test a vin-check algorithm.