VIN structure: WMI, VDS, VIS and the check digit

Two ways to divide the same 17 characters

The international standard, ISO 3779, splits a VIN into three sections. The US rule, 49 CFR Part 565, uses the same positions but treats the 9th character as a section of its own: the check digit.

For a shorter introduction, start with what is a VIN. This page goes section by section.

The WMI: positions 1 to 3

The first three characters identify the manufacturer and the type of vehicle. In the US, NHTSA has contracted SAE International to assign these identifiers to manufacturers, free of charge, and to check that a requested code isn’t already taken.

Small manufacturers get a shorter code. A 9 in position 3 means the manufacturer identifier is six characters long: positions 1–3 plus positions 12–14. For those makers, only positions 15–17 are the production number.

The VDS: positions 4 to 8

These five characters describe the vehicle. The rule says which attributes they must cover, but each manufacturer chooses the codes and their order:

• Passenger cars: make, line, series, body type, engine type, and every restraint device with its location.
• Multipurpose vehicles and trucks: attributes that depend on the type, such as engine type and gross vehicle weight rating (GVWR). Those rated at 10,000 lb or less must also code their restraint devices.

Because the codes are the maker’s own, the maker must send NHTSA the key to decode them at least 60 days before the first vehicle using them is offered for sale. That filing is what lets a public decoder, such as NHTSA’s vPIC or our VIN decoder, turn positions 4–8 into a model and an engine.

Position 7 has one more job on passenger cars and on trucks and multipurpose vehicles of 10,000 lb GVWR or less: a digit there points to a model year from 1980 to 2009, a letter to 2010 to 2039. The VIN year code page explains why.

The check digit: position 9

The 9th character is calculated from the other 16, after they’re all set. Its only purpose is to catch transcription mistakes. The method in 49 CFR 565.15:

1. Turn each character into a number. Digits keep their value. Letters use the table below.
2. Multiply each number by the weight for its position.
3. Add up the 16 results and divide the total by 11.
4. The remainder is the check digit. A remainder of 10 is written as X.

Worked example

Take the VIN 1C6RD6FT1CS310366. Converting each character and multiplying by its weight gives:

The products add up to 298. Divided by 11, that’s 27 with a remainder of 1, and the 9th character of the VIN is 1. The VIN passes. Change any one character, say a 3 misread as an 8, and the total changes, so the check usually fails.

The VIS: positions 10 to 17

• Position 10, model year. One character from a 30-code cycle. See the VIN year code chart.
• Position 11, plant. The factory that built the vehicle, coded by the maker.
• Positions 12–17, production number. The maker’s sequential number. For small manufacturers, 12–14 belong to the manufacturer code and 15–17 are the sequence.

On passenger cars, and on trucks and multipurpose vehicles of 10,000 lb GVWR or less, the last five characters must be digits. On other vehicles, the last four must be.

Rules for every character

• Exactly 17 characters, and no position may be left blank.
• Only capital letters A to Z, except I, O and Q, and the digits 0 to 9.
• No two vehicles built within a 60-year period, starting with the 1980 model year, may share a VIN.

VINs from outside North America

The check digit in position 9 and the model-year code in position 10 come from the North American rule. ISO 3779 sets the three-section layout but doesn’t require either one. A VIN on a car built for another market, Europe for example, may therefore fail the check-digit test without being wrong, and its 10th character may not be a year. If you’re looking at an imported car, compare the VIN with the title and the car itself rather than relying on the check digit alone.