VIN Check Digit Calculator
VIN 9th digit proof with verdict.
What it does
Every modern VIN carries its own proofreader. The ninth character encodes the other sixteen through transliteration and weights, modulo eleven with X standing for ten. Fakes and typos usually break the proof.
The tool above runs 49 CFR 565. With 1HGCM82633A004352 the sum is 311, mod eleven is 3, and the ninth holds 3 for Valid check digit. The classic 1M8GDM9AXKP042788 expects X and matches. Swapping the Honda ninth to 5 flips the same VIN to Invalid with expected 3.
Letters map by table, never by alphabet order: A through H run one to eight while J restarts at one, skipping I and O throughout with Q banned too. Weights descend eight to two with ten at eighth and zero at the check itself.
This page checks arithmetic only. It never clears theft, liens, floods, or odometers. Title and history services own those answers.
How to use
- Type the 17 character VIN.
- Skip I, O, Q which never appear.
- Read expected check first.
- Read actual ninth character.
- Read valid or invalid verdict.
- Run history and title checks separately.
Formula
- VIN
- 17 characters without I, O, Q.
- values
- Letter to number table plus digits as-is.
- weights
- 8..2 positional multipliers with 0 at ninth.
FMVSS 115 / 49 CFR 565 check digit with fixed transliteration and weights. At any I, O, Q, or short length there is no check to run. Pass confirms arithmetic, never title or theft status.
Worked example
Example: Honda VIN check
Defaults: Honda style 1HGCM82633A004352. No I, O, Q letters allowed.
- Inputs: 17 character VIN 1HGCM82633A004352.
- Transliterate letters to numbers per table.
- Weight positions 1-17 with 8..2 (9th weight 0).
- Sum 311, mod 11 is 3, so expect 3.
- Ninth holds 3: Valid check digit. Tool shows the same.
Reference table
| VIN | Expected | Call |
|---|---|---|
| 1HGCM82633A004352 | 3 | Valid check digit |
| 1HGCM82653A004352 | 3, holds 5 | Invalid check digit |
| 1M8GDM9AXKP042788 | X | Valid check digit |
| 2FACP8CF0LX215891 | 1, holds 0 | Invalid check digit |
| 1HGCM82633A00435X | 2, holds 3 | Invalid check digit |
Limits
- Arithmetic only. No history check.
- 17 chars required. Short VINs excluded.
- No I, O, Q handling beyond reject.
- Standards change. Confirm current rule.
Common mistakes
- Typing O for zero or I for one.
- Counting positions from zero.
- Forgetting X means ten.
- Reading pass as clean title.
- Skipping history on a pass.
Try it yourself
Quick checks. Answers sit tucked under each question.
Same VIN with ninth changed to 5?
Same math expects 3 while ninth holds 5: Invalid check digit.
1M8GDM9AXKP042788?
GM classic expects X and holds X: Valid check digit.
Questions
How is the VIN check figured?
Transliterated sum with weights mod 11 (10 gives X). Here expect 3.
Which position holds the check?
Ninth character. Here 3 matches, so Valid check digit.
How do letters become numbers?
Letters map per table: A1 B2 C3 D4 E5 F6 G7 H8 J1 K2 and on. I, O, Q never appear.
What are the weights?
Weights run 8,7,6,5,4,3,2,10,0,9,8,7,6,5,4,3,2 with zero at the check.
What does invalid mean?
Altered 5 instead of 3 gives Invalid check digit with expected 3.
Does pass clear a car?
No. Arithmetic only, never theft, lien, or history clearance.