Thunderbird Registry - VIN Check Digit Calculation

Check Digit Calculation

The Check Digit, position 9 in your 1981 or newer vehicle's VIN, is used by the factory, insurance companies, DMV offices, and law enforcement agencies to verify that a particular VIN is a valid one for that vehicle. It is calculated by the following method:

1. Each number in the VIN is given its mathematical equivalent value.

2. Each letter in the VIN is given a mathematical value based on the following table:

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

3. The assigned value of each VIN character is then multiplied by the position weight factor as specified in the following table:

Position	Weight Factor
1st................…8	10th................9
2nd..................7	11th................8
3rd...................6	12th................7
4th...................5	13th................6
5th...................4	14th................5
6th...................3	15th................4
7th...................2	16th................3
8th...............…10	17th................2
9th (ignored)

4. The resulting products are then added, and that total is divided by 11.

5. The numerical remainder is the check digit. If the remainder happens to be 10, X is used. Here is an example. The check digit has been designated as the question mark in the sample VIN of 1FAPP64R?LH123456.

VIN	1	F	A	P	P	6	4	R	?	L	H	1	2	3	4	5	6
Assigned Values	1	6	1	7	7	6	4	9		3	8	1	2	3	4	5	6
Weight Factor	8	7	6	5	4	3	2	10		9	8	7	6	5	4	3	2
*AV WF**	8	42	6	35	28	18	8	90		27	64	7	12	15	16	15	12

8 + 42 + 6 + 35 + 28 + 18 + 8 + 90 + 27 + 64 + 7 + 12 + 15 + 16 + 15 + 12 = 403

403 divided by 11 = 36, with a remainder of 7.

The check digit for this example vehicle is therefore 7.

1FAPP64R7LH123456

By the way, this "example vehicle" would translate to a 1990 (L) Thunderbird Super Coupe (model 64, engine R), produced at Lorain, Ohio (H).