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ISIN Checksum Validator

Math

Validate a 12-character ISIN (ISO 6166) via its Luhn-style mod-10 check digit and break it into its country code and security identifier

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About ISIN Checksum Validator

Paste an ISIN and get an instant Luhn-style mod-10 checksum result, the same structural check exchanges and custodian systems run before accepting a security identifier into a trade or settlement record. The country code and 2-letter prefix are broken out separately from the 9-character security identifier, and every letter in the first 11 characters is transliterated to its numeric value (A=10 through Z=35) exactly as the ISO 6166 standard specifies, before the Luhn algorithm runs over the resulting digit string. It's useful for catching a typo in a spreadsheet of holdings, sanity-checking an ISIN pulled from a PDF prospectus, or generating valid test identifiers for a trading system. Nothing is sent anywhere: validation runs entirely in your browser and no ISIN is stored or transmitted.

How to use ISIN Checksum Validator

  • 1.Paste or type a 12-character ISIN into the input, with or without spaces.
  • 2.Check the Luhn-style mod-10 checksum result to confirm the check digit matches what the country code and security identifier produce.
  • 3.Read the country code and security identifier breakdown to confirm the parsed structure matches what you expected.

Frequently asked questions

Does a passing checksum mean the security actually exists?
No. The Luhn checksum only confirms the 12 characters are internally consistent, the same first-line sanity check a custodian or exchange runs before a real security-master lookup, which this tool doesn't perform.
How are the letters in an ISIN turned into numbers for the checksum?
Each letter is transliterated to a two-digit number: A=10, B=11, and so on through Z=35, per ISO 6166. The resulting numeric string (digits stay as-is) is what the Luhn algorithm actually runs over.
Is this the same check digit algorithm as a credit card number?
Yes, once the letters are transliterated to digits, the check digit is computed with the same Luhn (mod-10, alternating doubling) algorithm used for credit card numbers.
Is my ISIN sent to a server?
No, validation runs entirely client-side in your browser. Nothing is transmitted or stored.

Use via API, SDK, or MCP

cURL# Free: 1,000 req/day · Pro: 10,000 req/day
curl -X POST https://api.utilix.tech/v1/tools/isin-validator \
  -H "Authorization: Bearer utx_live_..." \
  -H "Content-Type: application/json" \
  -d '{"isin":"US0378331005"}'

Get an API key from your dashboard · Full API docs →

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