Why does IBAN length differ between countries?

Each country sets its own BBAN (Basic Bank Account Number) format, which varies by how many digits it needs for bank, branch, and account number. Germany uses 22 characters, Norway 15, and Malta 31. The country code and 2 check digits are always the first 4.

What are the first four characters of an IBAN?

The first two letters are the ISO 3166 country code, and the next two digits are the MOD-97 check digits. The rest is the country-specific BBAN. So DE89 means Germany with check digits 89, followed by the German account details.

How does the MOD-97 check work?

Move the first four characters to the end, convert letters to numbers (A=10 ... Z=35), and compute the big number modulo 97. A valid IBAN gives a remainder of 1. Any other remainder means a transcription error.

Does the right length guarantee a valid IBAN?

No. Correct length is necessary but not sufficient. The MOD-97 check digits catch most single-character typos and digit swaps. This tool checks both length and check digits, but only the bank can confirm the account exists.

Should I store IBANs with spaces?

Store them without spaces in a single uppercase string. Spaces in groups of four are a display convention for humans. Always strip whitespace before validating or saving to a database.

IBAN Length by Country

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An IBAN’s length is fixed per country, from 15 characters in Norway up to 31 in Malta. This tool gives the official length and structure for each IBAN-participating country and validates any IBAN you paste against both its length and the MOD-97 check digits.

How it works

Every IBAN starts with the same four characters:

D E 8 9 3 7 0 4 0 0 4 4 0 5 3 2 0 1 3 0 0 0
^^ ^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ctry chk BBAN (country-specific)

Characters 1-2 — country code: ISO 3166-1 alpha-2.
Characters 3-4 — check digits: computed with MOD-97.
Remaining — BBAN: the national account number, whose length and layout the country defines.

To validate the check digits, move the first four characters to the end, replace each letter with two digits (A=10 … Z=35), and take the whole number modulo 97. A correct IBAN yields a remainder of exactly 1.

Tips and examples

GB (United Kingdom) IBANs are 22 characters: GBkk BBBB SSSS SSAA AAAA AA.
The check digits alone catch most typos, but a wrong country code makes the length check fail first — always confirm the leading two letters.
Strip all spaces and uppercase the string before validating; mixed case or stray spaces are the most common false-failure cause.