How a VIN is built

The US rule is 49 CFR Part 565. It says each VIN has seventeen characters, that a check digit is part of it, and that every character is a digit or one of the letters A B C D E F G H J K L M N P R S T U V W X Y Z — the alphabet without I, O and Q. The rule divides the seventeen positions into four sections:

The sections of a VIN under 49 CFR 565.15
Positions	Section	What it holds
1–3	First section. In the trade, the world manufacturer identifier (WMI).	The manufacturer and the type of vehicle. A manufacturer of fewer than 1,000 vehicles of a type each year has a 9 in position 3, and positions 12–14 complete its identifier.
4–8	Second section. In the trade, the vehicle descriptor section (VDS).	The vehicle’s attributes. For a passenger car: make, line, series, body type, engine type, and all restraint devices and their location. The manufacturer chooses the coding and files the key with NHTSA.
9	Third section.	The check digit: 0 to 9, or X.
10	Fourth section. In the trade, the vehicle identifier section (VIS).	The model year, as a code.
11		The plant of manufacture.
12–17		The number the manufacturer assigns in sequence in production. For a low-volume manufacturer, positions 15–17.

The regulation calls the parts “sections”; WMI, VDS and VIS are the names used with the ISO standards the VIN is based on. They do not divide the VIN identically: as Wikipedia describes the ISO scheme, the descriptor section runs from position 4 to position 9, where the US rule makes position 9 a section of its own.

The VIN check digit, step by step

The check digit exists, the rule says, “to provide a means for verifying the accuracy of any VIN transcription”. The calculation in 49 CFR 565.15(c) has four steps.

Give every character a value. A digit is worth itself. A letter is worth the value in the table below.
Multiply each value by the weight of its position. Position 9, where the check digit goes, has no weight.
Add the products and divide the total by 11.
The remainder is the check digit. A remainder of 10 is written X.

Values of the letters

Weights of the positions

Position first, then its weight. Position 9 is the check digit itself and is not weighed.

18
27
36
45
54
63
72
810
9—
109
118
127
136
145
154
163
172

The regulation’s own example

The rule works the sum for a sample VIN, 1G4AH59H?5G118341, where the question mark is the digit to be found:

The sample calculation in 49 CFR 565.15, Table VI
Position	Character	Value	Weight	Product
1	1	1	8	8
2	G	7	7	49
3	4	4	6	24
4	A	1	5	5
5	H	8	4	32
6	5	5	3	15
7	9	9	2	18
8	H	8	10	80
9	?	—	0	0
10	5	5	9	45
11	G	7	8	56
12	1	1	7	7
13	1	1	6	6
14	8	8	5	40
15	3	3	4	12
16	4	4	3	12
17	1	1	2	2

The products add up to 411. 411 ÷ 11 = 37 with a remainder of 4, so the check digit is 4 and the full VIN reads 1G4AH59H45G118341. Paste it into the decoder above to watch the same arithmetic.

If the check digit fails

Most often a character was misread or mistyped — that is what the digit is for. It does not by itself mean the VIN is false. The check digit is compulsory in North America and in China but not in Europe, so a VIN assigned outside the US rule can fail the test and be genuine. A passing check digit, in turn, proves only that the seventeen characters are consistent with each other, not that a vehicle with that VIN exists.

The model year in position 10

Thirty codes are used, in a cycle that repeats every thirty years: the letters A to Y without I, O, Q and U, then the digits 1 to 9. Each code therefore names two years in the tables of the rule, which run from 1980 to 2039:

A1980 · 2010
B1981 · 2011
C1982 · 2012
D1983 · 2013
E1984 · 2014
F1985 · 2015
G1986 · 2016
H1987 · 2017
J1988 · 2018
K1989 · 2019
L1990 · 2020
M1991 · 2021
N1992 · 2022
P1993 · 2023
R1994 · 2024
S1995 · 2025
T1996 · 2026
V1997 · 2027
W1998 · 2028
X1999 · 2029
Y2000 · 2030
12001 · 2031
22002 · 2032
32003 · 2033
42004 · 2034
52005 · 2035
62006 · 2036
72007 · 2037
82008 · 2038
92009 · 2039

Position 7 settles which. For a passenger car, and for a multipurpose passenger vehicle or truck with a gross vehicle weight rating of 10,000 lb or less, the rule says a digit in position 7 means the year is in the range 1980–2009 and a letter means 2010–2039. For other vehicles the VIN alone does not settle it; NHTSA’s decoder answers from what the manufacturer filed.

What the decoder returns, and its limits

NHTSA’s vPIC database is populated, NHTSA says, from the information manufacturers submit under Part 565, and that is what the Decode button reads. A field that comes back empty means NHTSA holds no data for it; NHTSA’s own note says it should not be read as the vehicle lacking that feature. The decoder describes the vehicle as built: it knows nothing of the car’s history, owners, mileage, accidents or title.

This page accepts only complete 17-character VINs. The 17-character form is what the rule requires today; Part 565 also requires that no two vehicles built within sixty years of the 1980 model year share a VIN.

Next: recalls for the model, owner complaints, its fuel economy — or all of them at once on the desk.

VIN decoder, with the check digit worked out

The decoder

The check digit, worked

The vehicle