IBAN Calculator (Generate + Validate)
Use this tool to generate IBAN check digits from a country code and BBAN, or validate a full IBAN with the standard MOD-97 algorithm.
What Is an IBAN?
An IBAN (International Bank Account Number) is a standardized way to identify a bank account across national borders. Instead of relying on country-specific formats, IBAN creates a common structure that helps banks route payments more accurately and with fewer errors.
IBANs are used heavily in Europe and many other regions for domestic and international transfers. The exact length differs by country, but the core layout is always the same: country code, check digits, and a BBAN (the local account identifier).
Basic IBAN Structure
- Country code (2 letters): ISO country identifier, such as DE, FR, GB, or ES.
- Check digits (2 numbers): mathematically computed using MOD-97.
- BBAN (country-specific): includes bank code, branch code, and account number details depending on local rules.
How This IBAN Calculator Works
This page includes two practical functions:
- Generate mode: You enter a country code and BBAN, and the calculator computes check digits.
- Validate mode: You enter a full IBAN and the calculator confirms whether it passes structural and checksum tests.
Generation Logic (Check Digits)
To generate check digits, the algorithm temporarily inserts 00, rearranges the string, converts letters to numbers
(A=10, B=11, ... Z=35), and computes the remainder modulo 97. The final check digits are 98 - remainder.
Validation Logic (MOD-97)
Validation uses the official approach: move the first 4 characters to the end, convert letters to numbers, then compute mod 97. A valid IBAN always returns a remainder of 1.
Why IBAN Validation Matters
A single typo in banking data can delay salary runs, vendor payouts, customer refunds, or cross-border settlements. Fast validation helps you catch format issues before a payment file reaches your bank.
- Reduces failed transfers and returned payments
- Lowers manual correction work in finance teams
- Improves customer trust and payment reliability
- Supports cleaner onboarding for suppliers and contractors
Common IBAN Entry Mistakes
- Confusing the letter O with the number 0
- Using an incorrect country code
- Missing or extra BBAN characters
- Copy/paste artifacts (hidden symbols, punctuation, line breaks)
- Relying on checksum alone without country-length checks
Practical Tips for Teams and Individuals
If you process payments often, standardize data collection and validation as early as possible:
- Store IBAN in a normalized format (no spaces) and display with grouped spacing for readability.
- Validate at entry time rather than waiting until payment day.
- Combine IBAN checks with account-holder verification where regulations require it.
- Re-validate old records before large payout batches.
FAQ
Does a valid checksum guarantee the account exists?
No. MOD-97 confirms structural correctness, not account ownership or account status. For that, banks and payment providers use additional verification systems.
Can IBAN lengths vary by country?
Yes. Each country has a fixed IBAN length. This calculator checks known country lengths and flags mismatches.
Should I include spaces when entering an IBAN?
Either works. The calculator strips spaces and non-alphanumeric separators before processing.
Bottom line: use the calculator above whenever you create or review account details for international transfers. A few seconds of validation can prevent expensive payment errors later.