ISIN Check Digit Calculator

How ISIN Check Digit Calculator Works?

The ISIN Check Digit Calculator converts the 11-character payload to digits. Letters become values from A = 10 to Z = 35. It then applies Luhn to that digit string. ISIN means International Securities Identification Number.

1. 1Enter the 2-letter country code and the 9-character National Securities Identifying Number (NSIN).
2. 2Replace each letter with its 2-digit value (A = 10 … Z = 35).
3. 3Double every second digit starting with the rightmost.
4. 4Add the digits of all values to get S.
5. 5Append (10 − (S mod 10)) mod 10 as the 12th character.

ISIN Check Digit Calculator Formula

The ISIN formula is Check = Luhn(num(CC + NSIN)), as defined in ISO 6166.

digits = num(CC ‖ NSIN),  A = 10 … Z = 35
Check = (10 − (LuhnSum(digits) mod 10)) mod 10

• CC is the country code.
• NSIN is the national identifier (CUSIP, SEDOL, WKN…).

Letters → numbers: US037833100 → 3028037833100
Luhn sum = 45
Check = 5
ISIN = US0378331005

ISIN Check Digit Calculator Conversion Table

The ISIN conversion table lists well-known securities with their NSIN and ISIN check digit.

What is ISIN Check Digit Calculator?

An ISIN Check Digit Calculator is a tool that computes the 12th character of an International Securities Identification Number. ISINs identify shares, bonds, funds, and derivatives worldwide.

An ISIN wraps a national identifier: a US ISIN contains a CUSIP, a UK ISIN contains a SEDOL. National Numbering Agencies (NNA) coordinated by ANNA issue ISINs.

What are the uses of ISIN Check Digit Calculator?

There are 3 main uses of the ISIN Check Digit Calculator, including trade capture, regulatory reporting, and reference data checks.

• Trade capture: Trading systems validate ISINs on order entry.
• Regulatory reporting: Firms check ISINs in MiFID II and EMIR reports.
• Reference data checks: Data vendors catch corrupted identifiers.