Free VIN Validation
VIN Check Digit Validator
Verify any 17-character VIN passes the ISO 3779 checksum used by every U.S.-market vehicle since 1981. Catch typos and forged VINs before you buy.
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How the VIN Check Digit Works
The 9th character of every 17-character VIN is a mathematical checksum derived from the other 16 characters. It exists to detect typos and forgeries. The algorithm is fixed by 49 CFR §565.15 and ISO 3779:
- Convert each character to a numeric value (0-9 for digits; 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).
- Multiply each character\u2019s value by its position weight. The weights for positions 1-17 are: 8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2. (Position 9 has weight 0 because it's the check digit being computed.)
- Sum all 17 products.
- Divide the sum by 11. The remainder is the check digit. If the remainder is 10, the check digit is the letter X.
This algorithm catches every single-character typo and most two-character transpositions. It's the same family of math used in ISBN book numbers and credit card Luhn checks.
Common VIN Errors This Catches
Confusing O and 0
VINs never contain the letter O. If you typed an O, replace it with the digit 0.
Confusing I and 1
VINs never contain the letter I. If you typed an I, replace it with the digit 1.
Confusing Q and 0 or 9
VINs never contain the letter Q. The character is usually the digit 0 or sometimes the digit 9.
Transposing adjacent characters
Swapping two neighboring characters changes the weighted sum and almost always fails the checksum.
Off-by-one transcription
Reading 5 as S, 8 as B, or 6 as G when copying from a sticker — the math will detect it.
Missing or extra character
A VIN with fewer or more than 17 characters fails the format check before the checksum even runs.
FAQ
What is the VIN check digit?
The check digit is the 9th character of every 17-character VIN. It's a mathematical checksum computed from the other 16 characters using a fixed weighting algorithm specified in 49 CFR §565.15. The check digit lets anyone verify a VIN is well-formed without consulting a database — typos in any of the other 16 positions will produce a different check digit and reveal the error.
How is the VIN check digit calculated?
Each character is converted to a numeric value (0-9 for digits, 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). Each position is multiplied by a fixed weight (positions 1-17 use weights 8,7,6,5,4,3,2,10,0,9,8,7,6,5,4,3,2). The 17 products are summed and divided by 11. The remainder is the check digit. If the remainder is 10, the check digit is "X."
Why don't VINs contain I, O, or Q?
These three letters are excluded by 49 CFR §565.15 because they look too similar to the digits 1, 0, and 0 respectively. Excluding them eliminates a common source of transcription errors. If you see a VIN with I, O, or Q, it's either a transcription error or not a real VIN.
Does NHTSA enforce the check digit?
For U.S.-market vehicles built since 1981, yes — manufacturers must submit VINs that pass the checksum. NHTSA's vPIC API will still attempt to decode VINs with bad check digits but flags them with error code 1 ("Check Digit (9th position) does not calculate properly"). Some pre-1981 vehicles and certain grey-market imports may have VINs that don't follow the standard.
Does a valid check digit mean the VIN is real?
No. The check digit only proves the VIN is mathematically well-formed. A VIN with a valid checksum could still be entirely fabricated — the digit math would just happen to work out. To confirm a VIN was actually issued by a manufacturer, decode it through NHTSA's database and verify the make, model, and year match the vehicle in front of you.
How do I find typos in a VIN?
If a VIN you typed manually fails the check digit test, the most likely causes are: (1) confusing 0 with O or 1 with I, (2) transposing two adjacent characters, (3) misreading 5 as S, 8 as B, or 6 as G. Re-check the characters one position at a time against the source. The check digit is in position 9 — count from the left.
When did 17-character VINs become standard?
The 17-character VIN became mandatory for vehicles built for U.S. sale starting January 1, 1981. Before that, VINs varied in length and format from manufacturer to manufacturer. The standard is governed internationally by ISO 3779 and in the U.S. by 49 CFR Part 565.
Valid VIN? Decode it.
Once you've confirmed the VIN passes the checksum, decode it for free to get the full vehicle spec and see what real buyers paid.