IBAN Calculator
Enter a national account number (BBAN) and get the full IBAN with correct check digits: for 89 countries.
Calculate an IBAN
Enter the national account details exactly as your bank formats them.
How this tool works
This tool is designed for testing, education and workflow prototyping. It validates or generates structurally correct values based on published format rules and clearly states where no live-bank lookup is performed.
From BBAN to IBAN
Your bank account has a national format (in Germany: 8-digit Bankleitzahl + 10-digit account number) and an international format: the IBAN. The IBAN is simply the national BBAN plus a country code and two check digits computed by the mod-97 algorithm. This calculator computes international check digits for a complete BBAN using the toolkit’s 89 supported formats. It does not derive every national field from a bare domestic account number or apply every bank’s conversion exceptions.
How the check digits are computed
- Take the BBAN and append the country code + “00” (e.g. 370400440532013000DE00).
- Convert letters to numbers (A=10 … Z=35).
- Compute the remainder mod 97, then check digits = 98 − remainder.
- Prepend country code + check digits to the BBAN. Done.
BBAN formats differ per country
Select a country above and the tool shows the exact expected format: for example, the UK needs a 4-letter bank code + 6-digit sort code + 8-digit account number, while France needs a 5-digit bank code + 5-digit branch + 11-character account + 2-digit RIB key. Enter the BBAN with no spaces for best results.
Important
- This calculates the structurally correct IBAN for given account details. Always confirm the result against your bank statement or online banking before using it for real transfers.
- Just need random test data instead? Try the IBAN generator.