IBAN Validator

Mod-97 arithmetic, not a database lookup

The validator follows ISO 13616 step by step: it strips spaces and uppercases the input, moves the first 4 characters (country code + check digits) to the end of the string, then converts every letter to a two-digit number (A=10, B=11, up to Z=35) while leaving digits untouched. The resulting decimal string, which can be dozens of digits long, is interpreted as one big integer and reduced modulo 97 using the ISO/IEC 7064 MOD97-10 scheme. The IBAN is valid only if that remainder is exactly 1.

That number is routinely far larger than JavaScript's safe integer range, so the tool computes the remainder with BigInt arithmetic rather than floating-point division, which would silently corrupt the result for longer IBANs. This is the same family of algorithm used to validate ISBNs and several national ID checksums: it is guaranteed to catch every single mistyped character and the overwhelming majority of adjacent-digit transpositions, which is exactly the class of error a person makes when copying a long number by hand.

• Rearrange: move the first 4 characters to the end.
• Convert letters to numbers: A=10 ... Z=35.
• Read the result as one decimal integer and take mod 97.
• Valid if and only if the remainder equals 1.

A valid checksum is not proof the account exists

Passing the mod-97 test only means the IBAN is internally consistent: right length for its country, right shape, and check digits that match. It does not confirm that the bank code inside the BBAN belongs to a real bank, that the branch exists, or that the account is open. Banks and payment processors still run the number against their own account database (or a live bank verification service) before moving money, this tool is the fast, offline first check that catches typos before they reach that stage.

The BBAN itself, everything after the first 4 characters, is not decoded into bank code, branch code and account number here on purpose: that internal layout is different for every one of the roughly 89 countries with a registered IBAN format, and getting it wrong would be worse than not showing it. The tool exposes the raw BBAN string so you can cross-check it against your bank statement.

Which countries use IBAN, and which don't

IBAN is mandatory for SEPA transfers across the European Union and the wider European Economic Area, and it has also been adopted well beyond Europe, by most of the Middle East, several Caribbean and Latin American countries, and a growing number of African nations. This tool's length table currently covers 89 countries, from Norway (the shortest format, 15 characters) to Russia (currently the longest at 33 characters).

Notably, the United States, Canada, Australia, China, India and Japan have not adopted IBAN. Banks in those countries identify accounts with their own domestic systems (for example, an ABA routing number plus account number in the US) and rely on a SWIFT/BIC code for international transfers instead. If you paste an account number from one of those countries here, it will correctly come back as an unrecognized or invalid format, since the string is not an IBAN to begin with.