What the check digit checks
For vehicles using the U.S. VIN check-digit rule, position 9 contains a digit from 0 to 9 or the letter X. Its value is calculated from the other characters. If one of those characters was copied incorrectly, the calculation will often expose the mismatch.
A match does not prove that a VIN is authentic, belongs to the vehicle in front of you, or has a clean history. A mismatch is a reason to check the original identifier and the applicable rules, not a worldwide verdict of invalidity.
How the calculation works
- Keep numbers at their numeric value. Convert letters using the values in the table below.
- Multiply each value by its position weight. The 17 weights are 8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2.
- Add all 17 products and take the remainder after division by 11.
- Use the remainder as the check digit. A remainder of 10 is represented by X.
| Value | Letters |
|---|---|
| 1 | A, J |
| 2 | B, K, S |
| 3 | C, L, T |
| 4 | D, M, U |
| 5 | E, N, V |
| 6 | F, W |
| 7 | G, P, X |
| 8 | H, Y |
| 9 | R, Z |
Position 9 has a weight of zero, so the character already printed there does not influence the expected result. I, O, and Q have no assigned value because they are not allowed VIN characters.
Worked example: a remainder of 4
The sample in 49 CFR § 565.15 is 1G4AH59H45G118341. Converting the characters and applying the weights produces a total of 411. Dividing 411 by 11 gives 37 with a remainder of 4. The ninth character is 4, so this sample matches the calculation.
What a mismatch means for an international VIN
VIN conventions and legal requirements differ across markets. This site can calculate the U.S. formula without assuming that the formula is required for every submitted vehicle. It preserves the character breakdown and available decoded information even when a check-digit warning is present.
First recheck the plate and documents. If they agree and the vehicle was built for another market, consult the manufacturer’s VIN documentation. Do not replace the ninth character just to make a calculation pass: that would change the VIN you are looking up.