Check digit validator
Is this VIN well-formed?
Position 9 of a VIN is a checksum computed from the other sixteen characters. It catches most typos. This runs entirely in your browser — nothing is sent anywhere.
What a failed check digit does and does not mean
A failure is a warning, not a verdict.
A mismatch usually means a transcription error — a character misread off a windshield plate, or a digit transposed. Re-reading the VIN fixes most of them.
But the check digit is only mandatory for vehicles built for the North American market. Vehicles manufactured for other markets are not required to carry a valid one, so a grey import can fail this test and still be a perfectly genuine VIN.
A valid check digit also does not mean the VIN belongs to a real vehicle. It means the seventeen characters are internally consistent. Decode it to find out whether a vehicle exists behind it.
Algorithm defined in 49 CFR 565. See how the check digit works.
How the check works
A VIN has exactly 17 characters. Federal rules in 49 CFR Part 565 allow only the digits 0 to 9 and the letters A to Z without I, O and Q, because those three are too easy to confuse with 1 and 0. If you type one of them here, the validator reads it as the digit it most likely is and tells you it did.
The 9th character is computed from the other sixteen in four steps:
- Each letter is converted to a number from a fixed table, so A is 1, B is 2 and H is 8. Digits keep their own value.
- Each value is multiplied by a weight for its position. The weights run 8, 7, 6, 5, 4, 3, 2 for positions 1 to 7, then 10 for position 8. Position 9 is skipped, and positions 10 to 17 run 9 down to 2.
- The sixteen products are added together and the total is divided by 11.
- The remainder is the check digit. A remainder of 10 is written as the letter X.
The validator does that sum and compares the result with the 9th character you entered. Our guide to how the check digit works walks through the full letter table with an example.
Why a VIN fails the check
Most failures come from copying the VIN, not from the VIN itself. The usual causes are:
- a character misread from the windshield plate, such as 8 and B, 5 and S, or 2 and Z;
- two characters swapped, or one skipped and another doubled;
- a VIN copied from a document that already had a typo in it.
Read the VIN again from the vehicle itself, ideally from two places such as the windshield plate and the door jamb label. Our guide to where to find the VIN lists the places to look.
If it still fails, consider where the vehicle was built for. The check digit is only required on vehicles made for the North American market, so a genuine import can fail. A VIN that fails on a car sold new in the US deserves a closer look, and our guide to VIN cloning and fraud covers what to check next.
What to do after it passes
A passing check digit means the seventeen characters agree with each other. It does not tell you which vehicle they belong to. Decode the VIN to see the year, make, model and specifications its manufacturer registered, and the safety recalls NHTSA lists for that model. If the decoded vehicle does not match the car in front of you, treat that as a warning sign. Our guide to why a VIN won't decode explains the other reasons a lookup can come back empty.
Quick answers
What does the check digit on a VIN do?
It is the 9th character, calculated from the other sixteen. If one of them is copied wrong, the calculation usually stops matching, so the check digit flags most typing and reading errors.
Does a failed check digit mean the VIN is fake?
No. Most failures are a misread or mistyped character. Vehicles built for markets outside North America are not required to carry a valid check digit, so a genuine imported vehicle can fail.
Does a valid check digit prove the VIN is real?
No. It only shows the seventeen characters are consistent with each other. Decode the VIN to see whether a manufacturer has a matching vehicle on record.
Is the VIN I enter sent anywhere?
No. This validator runs entirely in your browser. To get specifications and recalls, you choose to decode the VIN separately.