How many numbers are in a VIN? Seventeen characters, and not all of them numbers

How many numbers are in a VIN, block by block

The federal rule, 49 CFR Part 565, fixes the count at seventeen and limits what can go in each place: the digits 0 to 9 and 23 capital letters. That makes 33 possible characters, printed in a capital sans-serif face at least 4 mm tall on the plate you read through the windshield by the left pillar.

Only the tail has to be numeric. On a passenger car, a multipurpose vehicle or a truck up to 4,536 kg (10,000 lb) gross weight, positions 13 to 17 must be digits. Everywhere else a letter is allowed.

• 1 to 3: the World Manufacturer Identifier, naming the maker, make and vehicle type
• 4 to 8: the vehicle attributes, which for a passenger car means line, series, body type, engine type and restraint devices
• 9: the check digit, a number from 0 to 9 or the letter X
• 10: the model year
• 11: the assembly plant
• 12 to 17: the production sequence number

Small makers use part of the serial

A manufacturer building fewer than 1,000 vehicles a year identifies itself with positions 12 to 14 as well as 1 to 3. Its own sequence number is left with the last three places.

Why a VIN never contains I, O or Q

The letter set in the rule leaves out I, O and Q. They are too easy to mistake for the numerals 1 and 0.

Use that when a plate is worn or a photo is blurred. A round character is a zero. An upright stroke is a one.

Position 10 is stricter still. The regulation’s year table also skips U, Z and the digit 0, so 2026 is T and 2027 is V, and the whole VIN 10th digit year chart follows the same pattern. The cycle repeats every 30 years, so an A can mean 1980 or 2010. The rule settles it with position 7: a letter there points to 2010 through 2039. When NHTSA rewrote Part 565 in 2008 it also stretched the no-duplicates period from 30 to 60 years, counted from the 1980 model year.

When a VIN has fewer than 17 characters

Age is the usual reason. VINs first appeared on US cars in 1954, and until the mid-1960s each maker, sometimes each division, wrote its own format. Many amounted to a serial number and little else. By January 1969 US cars carried a 13-character number, and the 17-character layout arrived with the 1981 model year.

Japan is the other exception. Japanese carmakers identify home-market cars by a frame number and a model code instead of a 17-character VIN, and those codes are absent from export versions of the same car. An imported home-market car can reach you with no VIN at all. Our guide to VIN vs chassis number covers how catalogs take a frame number instead.

How the check digit catches a mistyped VIN

Position 9 is arithmetic. Each letter gets a value, so A and J count as 1, B, K and S as 2, and so on. Each position gets a weight: 8, 7, 6, 5, 4, 3, 2 and 10 across positions 1 to 8, then 9 down to 2 across positions 10 to 17. Multiply, add the products and divide the total by 11. The remainder is the check digit, and a remainder of 10 is written as X.

The regulation’s own worked example is 1G4AH59H45G118341. Its weighted sum is 411, and 411 divided by 11 leaves 4, the character sitting in position 9. Mistype one character and the sum moves, so the remainder usually stops matching.

Usually, because some characters share a value. The digit 1 and the letters A and J all count as 1, so a swap between them passes the sum. The check digit catches slips of the finger, and look-alikes still need a second look at the plate.

It also depends on the market. The check digit is compulsory in North America and China and not in Europe, so a European-market VIN that fails the sum can still be the car’s real number. NHTSA’s decoder reports a failure as “Check Digit (9th position) does not calculate properly”. Our free VIN decoder runs the same sum in your browser and rejects I, O, Q and any length other than 17.

Count it before you order parts

A parts catalog decodes whatever VIN you type, typos included. Count to 17, look for an I, O or Q, and run the check digit on a North American car before you trust the build it shows. If the number passes and the catalog still names the wrong model, compare the plate with a second place the car carries its VIN. Our guide on how to read a VIN walks through each block with real examples.