VIN Check Digit Calculator
By CheckMyVIN · Data source: NHTSA vPIC · Updated July 5, 2026
Paste a VIN from a listing, title, or auction sheet and confirm its 9th character validates. A mismatch means a typo — or a VIN that was never real. It takes seconds and runs entirely in your browser.
Type or paste a VIN to check its 9th-position check digit.
How the check digit works
Every 17-character VIN carries its own error-detection code in position 9, defined by the ISO 3779 standard and mandated for US-market vehicles by 49 CFR Part 565. The math has three steps:
- Transliterate each character to a number. Digits are themselves; letters map A=1, B=2 … H=8, J=1, K=2 … R=9, S=2 … Z=9 (the letters I, O, and Q are never used in a VIN).
- Weight each position by a fixed factor: 8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2. Position 9 — the check digit itself — has weight 0, so it never affects its own calculation.
- Sum, divide by 11, take the remainder. A remainder of 0–9 is the check digit; a remainder of 10 is written as the letter X.
Because a single wrong character changes the weighted sum, the check digit catches the overwhelming majority of one-character typos and transpositions — which is exactly why it exists. It is a ISO 3779 checksum, not a security feature.
What a check digit catches — and what it can't
A passing check digit tells you the VIN is well-formed: copied correctly and mathematically consistent. That's genuinely useful for spotting a mistyped VIN in a listing or a number invented on the spot. But it is a low bar, and a careful seller of a bad car will hand you a VIN that validates perfectly.
The check digit cannot tell you whether the car was in a crash, carries a salvage or flood title, has had its odometer rolled back, or whether the VIN was cloned from another genuine vehicle. None of that is encoded in the 17 characters. The next step after a valid check digit is to decode the VIN for free against the official NHTSA database — that gives you the real make, model, year, engine, plant, and every open recall — and then, if you're buying, a full vehicle history report for accident and title records.
Frequently asked questions
What is the VIN check digit?
The check digit is the 9th character of a 17-character VIN. It is a single digit (0–9) or the letter X, computed from the other 16 characters using the ISO 3779 / 49 CFR Part 565 formula. Its only job is to catch errors: if one character is mistyped or a VIN is fabricated at random, the 9th character almost always stops matching the math.
Does a valid check digit mean the car is clean?
No. A valid check digit only means the 17 characters are internally consistent — that the VIN was copied correctly and is well-formed. It says nothing about accidents, salvage or flood titles, odometer rollback, or whether the VIN was cloned from another real car. Those require a decode against official records plus a full vehicle history report.
Why did my real VIN fail the check digit test?
Two common reasons. First, a typo — recheck it character by character against the dashboard plate, door-jamb label, or title. Second, some low-volume, grey-market, or pre-standard vehicles were not built to the North American check-digit rule, so a genuine VIN can fail the math. If the VIN is from a US-market car and still fails after careful re-entry, treat it as a red flag and verify with the seller.
Can the check digit be X?
Yes. The formula sums the transliterated characters times their position weights, divides by 11, and takes the remainder. A remainder of 10 cannot be written as a single digit, so it is represented by the letter X. This is the only place the letter X legitimately appears as a check digit.
Is this calculator free and private?
Yes. The calculation runs entirely in your browser using the public ISO 3779 algorithm — nothing is sent to a server, and there is no signup. If the VIN is valid you can decode its free NHTSA report in one click.
Keep reading
New to VINs? Start with what each VIN position means, or decode the model year with the VIN year code chart. When you're ready, run any VIN for a free report.
About this guide
CheckMyVIN generates free vehicle reports for cars sold or titled in the US, using official NHTSA data — VPIC specifications plus live recall records. This guide is reference material maintained alongside the tool: no signup, no paywall. More about CheckMyVIN →