### The Check Digit

borgo has done an excellent job of detailing the specifics on a VIN number and how they relate to what's actually on the vehicle or the options the vehicle has. Let's take a look at one of the lesser known numbers which make the whole thing work properly.

In position 9 of the VIN number is a character called
a check digit. This character can be any number between
0 and 9, or X. To get this check digit, we preform the calculations below:

In our example, we'll use the VIN number **JT2MA71N2M0155441**

Don't worry, this vin is completely fictional, but correct. You can head over to carfax and punch it in and it should come back with 0 records.

**Step 1**:

First, convert every letter in the vin, to it's associated number. Any numbers in the original remain the same in their same place.

A = 1; B = 2; C = 3; D = 4; E = 5; F = 6; G = 7; H = 8;
J = 1; K = 2; L = 3; M = 4; N = 5; O = 6; P = 7; R = 9;
S = 2; T = 3; U = 4; V = 5; W = 6; X = 7; Y = 8; Z = 9;

**Step 2**:

Now you must multiply each of the 17 digits in the vin
by a set "weight" or multiplyer. The multiplyer is
Position Specific.

1st = 8; 2nd = 7; 3rd = 6; 4th = 5; 5th = 4; 6th = 3; 7th = 2;
8th = 10; 9th = 0; 10th = 9; 11th = 8; 12th = 7; 13th = 6; 14th = 5;
15th = 4; 16th = 3; 17th = 2;

**Step 3**:

After multiplying all of the digits by their weight, you should come out with a sum for each number. Add all of the sums together, then divide by 11. The remainder of the answer divided by 11 is the check digit. If the remainder is '10' the check digit is 'X'

Here's our example:

VIN J T 2 M A 7 1 N 2 M 0 1 5 5 4 4 1
Assigned Values 1 3 2 4 1 7 1 5 2 4 0 1 5 5 4 4 1
Multiplyer 8 7 6 5 4 3 2 10 0 9 8 7 6 5 4 3 2
SUM 8 21 12 20 04 21 02 50 00 36 00 07 30 25 16 12 02
Add them all together: 266
Divide by 11: 24
266 - 11 * 24 = Remainder of 2
2 matches position 9 within the VIN. Therefore, the VIN
is correctly entered.

That's how the check digit works folks! It's not any type of security system, just a method to keep people from punching in a vin number incorrectly; since if you enter it incorrectly, the check digit will be different. It's similar to the one that's in use with your credit cards.

The example VIN that I provided was originally a VIN number that's had it's sequence number changed and the check digit recalculated. The number is useless, except the check
digit is correct; so you can run it through carfax and
other VIN reporting software and it won't give you an error. I don't think you can take it to the DMV and
get a vehicle registered with it.