VIN Tool

VIN Check Digit Calculator

Q: What is the VIN check digit?

The 9th character of a VIN is calculated using a weighted algorithm. It validates that the other 16 characters are correct and unaltered.

Q: How is the check digit calculated?

Each VIN character is assigned a numeric value and multiplied by a position weight. The sum is divided by 11, and the remainder is the check digit (0-9 or X for 10).

Q: Why does the check digit matter?

A mismatched check digit indicates the VIN may have been altered or entered incorrectly — a potential fraud indicator. Run a full VIN check →

Calculate the check digit (position 9) of any VIN to verify its validity using the official NHTSA algorithm.

Position 9 of every VIN is a check digit — a mathematical validation that confirms the VIN has not been altered. Use this tool to verify any VIN's integrity. VIN length guide →

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How the Check Digit Algorithm Works

The mathematics behind VIN position 9.

The VIN check digit uses a modulus-11 algorithm defined by the US Department of Transportation:

Each VIN character is converted to a numeric value (A=1, B=2... letters I, O, Q excluded)
Each position has a weight factor (8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2)
Multiply each value by its weight and sum all products
Divide the sum by 11 — the remainder is the check digit
If remainder is 10, the check digit is X

Verify any VIN. Free VIN decoder → | Full history — $5 →

Learn more about the ISO 3779 VIN standard and model year codes.

Check Digits and Fraud Detection

How position 9 catches altered VINs.

The check digit serves as a built-in fraud detection mechanism. If someone alters any character in the VIN — to disguise a stolen vehicle or hide a salvage title — the check digit will no longer validate. This is why law enforcement uses check digit verification as a first step in VIN fraud investigations.

When buying a used car, verifying the check digit takes seconds and catches crude VIN tampering. For deeper verification, a vehicle history report ($5) cross-references the VIN against national databases.