Canadian · Validation
ISIN validator & check digit calculator.
Verify a 12-character ISIN's real check digit, or enter just the 11-character body (country code + NSIN) to have the correct check digit computed for you. Everything runs in your browser: nothing you type is transmitted anywhere.
Inputs
Result
Enter an ISIN and press Validate.
How the ISIN check digit works
An ISIN is 12 characters: a 2-letter ISO 3166 country code, a 9-character alphanumeric National Securities Identifying Number (NSIN), and 1 numeric check digit — all defined by ISO 6166. The check digit is computed with a "double-add-double" variant of the Luhn algorithm: every letter in the first 11 characters is converted to two digits (its ASCII code minus 55, so A = 10 through Z = 35), digits are left as-is, and the whole thing is concatenated into one long digit string. The standard Luhn algorithm is then applied to that string — starting from the rightmost digit, every second digit is doubled (subtracting 9 if the result exceeds 9), every digit is summed, and the check digit is whatever value makes the total a multiple of 10.
Apple Inc.'s real ISIN, US0378331005, is the worked example published alongside the algorithm: the first 11 characters "US037833100" become the digit string "3028037833100" (U = 30, S = 28), the Luhn sum is 45, and (10 − 5) mod 10 = 5 matches the real check digit.
What a passing checksum does and doesn’t tell you
A valid check digit only proves the characters are internally consistent — it does not confirm the ISIN was ever actually assigned to a real security, or identify what that security is. For that, look the number up with your broker or a service like the ISIN database maintained by ANNA (the Association of National Numbering Agencies). This tool runs entirely in your browser: nothing you type is transmitted, stored, or logged.