IBAN Check Digit Calculator

Calculate correct check digits using the MOD-97 algorithm or verify existing IBANs. Educational tool with step-by-step calculation breakdown.

Calculate Check Digits

Select the country

Expected length: 18 characters

Format: 8n 10n
Example: DE89 3704 0044 0532 0130 00

About MOD-97 Algorithm

The MOD-97 algorithm is used to calculate and verify IBAN check digits according to ISO 13616 standard.

How it works:
  1. Replace the check digits with "00" in the IBAN
  2. Move the first 4 characters to the end
  3. Replace each letter with its numeric equivalent (A=10, B=11, ..., Z=35)
  4. Calculate the remainder when divided by 97
  5. Subtract the remainder from 98 to get the check digits
Verification:

To verify an IBAN, perform the same calculation. If the final MOD 97 result equals 1, the IBAN is valid.

💡 Why MOD-97?
The MOD-97 algorithm can detect up to 99% of transcription errors, including single digit errors, transposition of adjacent digits, and most other common mistakes.