check iban calculator

What this check IBAN calculator does

This tool helps you quickly verify whether an International Bank Account Number (IBAN) is structurally valid. It also calculates IBAN check digits when you provide a country code and BBAN. That makes it useful for payment setup, software testing, and data quality checks.

The validator follows the official ISO 13616 and MOD-97 algorithm used by banks and payment processors. In plain terms, it checks whether the IBAN format and checksum are mathematically correct.

How IBAN validation works

Step 1: Normalize the input

The validator removes spaces and converts letters to uppercase. So de89 3704 0044 0532 0130 00 becomes DE89370400440532013000.

Step 2: Basic format and length checks

Every IBAN starts with:

• 2-letter country code (like DE, FR, GB)
• 2 check digits (00–99)
• Country-specific BBAN section

The calculator compares total IBAN length against known country standards when available.

Step 3: MOD-97 checksum test

The first 4 characters move to the end, letters are converted to numbers (A=10, B=11, ..., Z=35), and the huge numeric string is divided by 97. A valid IBAN leaves remainder 1.

How to calculate IBAN check digits

If you already have a BBAN and country code, this page can compute the two IBAN check digits:

• Set check digits as 00
• Move country code and 00 to the end
• Convert letters to numbers and run MOD-97
• Check digits = 98 - remainder

The result is returned as a full IBAN and formatted in groups of 4 characters for readability.

Common IBAN mistakes this tool helps catch

• Wrong check digits after manual entry
• Typos in the BBAN section
• Incorrect country code
• Invalid length for specific countries
• Extra symbols copied from documents

Important note

Structural validity does not guarantee the account exists or can receive transfers. It only means the IBAN is mathematically valid. Always confirm beneficiary details through official banking channels before sending money.

Best practices when using IBANs in workflows

For individuals

• Paste IBANs directly from official invoices or banking apps
• Double-check country code and first 6–8 characters before payment
• Run a checksum test before authorizing large transfers

For teams and developers

• Validate IBAN format on form input (client side and server side)
• Store values normalized (no spaces, uppercase)
• Display grouped format for better readability in UI
• Log failed validations for data-quality monitoring