The VIN Check Digit

Position 9 of a VIN is a check digit: a number computed from the other sixteen characters that catches a mistyped or transposed VIN. It is defined by 49 CFR 565.15 and it is the one part of a VIN you can verify without any database at all.

How it is computed

1. Transliterate. Digits keep their value. Letters map to numbers: 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.
2. Weight each position by the table below. Position 9 weighs 0 — the check digit cannot contribute to computing itself.
3. Sum the products and take the remainder mod 11. That remainder is the check digit; a remainder of 10 is written as X, because a single VIN position cannot hold two characters.

Worked example: 5UXFA13564LU32275

358 mod 11 = 6, so the check digit is 6 — which is what position 9 of 5UXFA13564LU32275 holds.

Source: 49 CFR 565.15. The arithmetic above is computed live by @vinfoundry/core, the same code that validates VINs elsewhere on this site — it cannot drift from what the site does.