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VIN

General

Vehicle Identification Number

A 17-character code that uniquely identifies a motor vehicle, encoding the manufacturer, attributes, and production sequence with a built-in check-digit.

Definition

A Vehicle Identification Number (VIN) is a 17-character alphanumeric code that uniquely identifies an individual motor vehicle — car, truck, motorcycle, or trailer — encoding its manufacturer, key specifications, and production sequence. Standardized internationally under ISO 3779, the VIN is used for vehicle registration, insurance, recalls, theft recovery, and ownership history checks (such as accident or title records).

A VIN splits into three sections: the World Manufacturer Identifier (WMI) (characters 1–3), the Vehicle Descriptor Section (VDS) (characters 4–9, including a built-in check digit at position 9), and the Vehicle Identifier Section (VIS) (characters 10–17, encoding model year, assembly plant, and a sequential serial number).

Formula

The VIN's 9th character is a check digit, computed using a weighted-sum algorithm defined by the US Department of Transportation (adopted in the ISO/NHTSA standard):

  1. Convert every letter in the VIN to a numeric value using a fixed transliteration table (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, P=7, R=9, S=2, T=3, U=4, V=5, W=6, X=7, Y=8, Z=9 — note I, O, and Q are excluded entirely and never appear in a VIN).
  2. Multiply each of the 17 character values by its fixed positional weight (8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2 — position 9, the check digit itself, is weighted 0 during verification).
  3. Sum all 17 products and take the remainder when divided by 11.
  4. The check digit is that remainder, except a remainder of 10 is represented by the letter X.

Worked Example

A structurally valid VIN example, illustrative and fictional: 1HGCM82633A004352, where position 9 (the digit 3) is the check digit computed from the surrounding 16 characters.

Key Things to Know

  • 17 characters, no I/O/Q: those three letters are excluded everywhere in a VIN to avoid confusion with 1, 0, and 9 — check formatting with the VIN Validator.
  • Weighted mod-11 checksum: unlike a simple Luhn check, VIN validation uses fixed positional weights and a mod-11 formula, with X representing a remainder of 10.
  • Three encoded sections: WMI (maker/country), VDS (attributes + check digit), and VIS (year, plant, serial number) — a VIN decoder can extract meaningful vehicle data from these positions.
  • Globally unique for 30 years: model-year codes cycle every 30 years, meaning very old and very new vehicles can theoretically share a model-year character, though the full VIN combination remains distinct.
  • Standardized like other product identifiers: VIN's role for vehicles parallels what GTIN does for retail products — a fixed-length, checksum-verified code that follows the item throughout its lifecycle.
  • US-mandated check digit: the weighted mod-11 check digit specifically at position 9 is a US/NHTSA requirement; some other countries using the 17-character ISO format do not enforce the same check-digit rule.

Related Terms

GTINGlobal Trade Item NumberDUNS NumberData Universal Numbering System Number

Frequently Asked Questions

The 9th character of a VIN is a check digit computed by converting every character to a numeric value, multiplying each by a fixed positional weight, summing the results, and taking the remainder when divided by 11 — a remainder of 10 is represented by the letter X. You can verify a VIN against this formula with the [VIN Validator](/validators/vin-validator/).
A 17-character VIN splits into the World Manufacturer Identifier (WMI, characters 1–3, identifying the maker and country), the Vehicle Descriptor Section (VDS, characters 4–9, encoding body style, engine, and model attributes, including the check digit at position 9), and the Vehicle Identifier Section (VIS, characters 10–17, encoding model year, plant code, and a sequential production number).
The letters I, O, and Q are never used anywhere in a VIN, specifically because they are easily confused with the digits 1, 0, and 9. This is the same design principle used in other identifier systems, such as excluding lookalike letters from the [Medicare ID](/glossary/medicare-id/).
The 17-character VIN format was standardized internationally by ISO 3779 in 1981 and is used globally, though the specific meaning of characters within the VDS and VIS sections can vary by manufacturer and region. Vehicles built before the mid-1980s in some countries may have shorter, non-standardized VIN formats.
No, a VIN is designed to be globally unique to a single vehicle for its entire production run and lifetime — the combination of manufacturer code, model attributes, and sequential production number prevents duplication within any 30-year cycle, after which model-year codes are permitted to repeat.