Check whether an IBAN is valid using the mod-97 checksum.
Checked locally in your browser.
How do you validate an IBAN?
Move the first four characters to the end, convert letters to numbers (A=10 … Z=35), and the IBAN is valid when the whole number mod 97 equals 1, alongside a per-country length check. A passing checksum confirms the number is correctly formed but does not prove the account exists. GB82 WEST 1234 5698 7654 32 is a valid example IBAN.
Understanding your result
A passing checksum confirms the number is correctly formed. It does not prove the account exists or is open.
Formula and method
Move the first four characters to the end, convert letters to numbers (A=10 … Z=35) and the IBAN is valid when the whole number mod 97 equals 1.
Assumptions and limitations
The validator confirms the format is correct: it runs the mod-97 checksum and checks the length for the country code. It cannot confirm the account exists, is open or belongs to anyone, and it does not verify that the branch or bank code maps to a real institution. A pass means well-formed, not payable.
Worked example
GB82 WEST 1234 5698 7654 32 is a valid example IBAN.
How to use this tool
- Paste the IBAN (spaces are ignored).
- See whether it is valid and well-formed.
Common mistakes to avoid
- Including the wrong number of characters — each country has a fixed IBAN length.
About the IBAN Validator
Check whether an IBAN (International Bank Account Number) is correctly formed. The validator runs the official mod-97 checksum and the per-country length check.
Who should use this tool
Anyone entering or verifying bank details for international payments.
Benefits
- Catch mistyped IBANs before submitting a payment
- Run the official mod-97 checksum in one step
- Check per-country length without a reference table
- Validate sensitive account numbers with nothing uploaded
Practical use cases
- Verify a customer's IBAN before saving it
- Validate account numbers in a payment form
- Spot transposed digits in a manually copied IBAN
- Check example IBANs while building banking integrations
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Frequently asked questions
Does a valid IBAN mean the account is real?
No. It confirms the format and checksum only, not that the account exists.
Is my IBAN sent anywhere?
No. The check runs entirely in your browser.
Which countries does the length check cover?
The tool checks the IBAN against the expected length for its two-letter country code, since each country defines a fixed length. If a country code is unrecognised or the length is wrong, validation fails before the checksum stage, flagging the number as malformed rather than simply mis-typed.