IBAN Calculator: Convert BBAN to IBAN

IBAN Calculator Inputs and Results

The calculator needs the complete national BBAN, not only an account number. Which fields belong inside the BBAN depends on the selected country. The tool checks the stored length and broad character pattern, places the country code and temporary 00 check digits after the BBAN, converts letters to numbers, applies MOD-97, and subtracts the remainder from 98.

The synthetic example demonstrates the calculation flow and may not satisfy every domestic banking rule. Do not use it for a transfer, beneficiary record, account verification, or ownership claim.

How to Use the IBAN Calculator

First select the country that issued the domestic banking details. Then enter the complete BBAN in electronic form: letters and digits only, with no spaces, country prefix, or international check digits. The hint below the field shows the required length and a compact character pattern for the selected country. Press Calculate IBAN to create the two check digits and see both print and electronic formats.

A BBAN is not always the same as the account number shown by itself. Depending on the country, it may also contain a bank identifier, branch or sort code, account field, and one or more domestic check characters. If the value is too short, do not pad it with guessed zeros. Obtain the complete domestic structure from the bank, recipient, official statement, or another authoritative source.

1. Choose the issuing countryThe country determines the total IBAN length and BBAN pattern.
2. Enter the complete BBANExclude the two-letter country code and the two international check digits.
3. Calculate and reviewCopy the electronic form only after comparing every character with bank-issued details.

How BBAN to IBAN Conversion Works

An IBAN begins with a two-letter country code and two international check digits. The rest is the Basic Bank Account Number defined by that country's national format. To calculate the check digits, the calculator appends the country code and 00 to the BBAN, replaces each letter with its numeric value from A=10 through Z=35, and processes the resulting number with ISO 7064 MOD-97-10. The check digits are 98 minus the final remainder, padded to two digits.

The completed IBAN is checked again. Moving the first four characters to the end and applying MOD-97 must produce a remainder of 1. This second pass catches implementation mistakes in the calculator itself. It still answers only a mathematical question: whether the supplied characters can form a checksum-consistent IBAN under the stored country structure.

What This IBAN Calculator Can and Cannot Verify

The tool verifies a supported country, expected total length, broad BBAN letter-or-digit pattern, and the international checksum. It can help developers test forms, create documentation examples from synthetic BBANs, confirm a check-digit implementation, or normalize an IBAN into print and electronic display. All calculation happens in the browser and the entered BBAN is not submitted to an application endpoint by this tool.

The calculator does not query a live bank or branch directory. It cannot confirm that a bank code is currently assigned, a branch is active, an account exists, the account belongs to a named recipient, or a payment will succeed. Some countries also enforce domestic checks that go beyond the broad pattern stored here. Use an appropriate bank-connected validation or recipient-verification process for production payments.

• Format and MOD-97 consistency: supported
• Live bank, branch, and account status: not supported
• Account holder or beneficiary confirmation: not supported
• Payment, direct-debit, or fraud approval: not supported

IBAN Calculator Example

For a German example, select Germany and enter an 18-digit BBAN. The first eight digits represent the bank-code field and the remaining ten characters represent the account field. The calculator adds DE, calculates the two check digits, and returns a 22-character German IBAN. Print format groups the value for reading, while electronic format removes all spaces.

Use the synthetic-example button when you need to test the interface rather than a real account. Change one BBAN character and calculate again: the international check digits should change. Shorten the value or place a letter in a numeric-only field to see the invalid-length and invalid-pattern states. These cases are useful when comparing a front-end implementation with a server or test-suite implementation.

Common BBAN Input Errors

The most common error is pasting a complete IBAN into the BBAN field. Remove the first four characters before calculating: two country letters and two international check digits. Another common error is entering only the local account number while omitting the bank identifier, branch code, sort code, or domestic check characters required by the national format.

Do not translate letters into numbers yourself and do not include separators. The calculator normalizes lowercase letters, but it rejects punctuation and checks the selected country's broad character positions. If you have a complete IBAN and want to inspect or validate it, use the IBAN Decoder or IBAN Checker instead of recalculating from the BBAN.

Privacy and Production Safety

BBAN-to-IBAN calculation runs in browser JavaScript. The tool code does not send the BBAN or calculated IBAN to our application server. Normal hosting, security, analytics, consent, or advertising systems may still process technical information such as IP addresses, cookies, and browser identifiers as described in the Privacy Policy. Avoid entering personal financial data unless you have authority and a valid purpose.

For software development, prefer clearly labeled synthetic data and keep it outside production payment systems. A checksum-valid result can accidentally resemble a real account because there is no universal test-only IBAN range. Never initiate a transfer, create a beneficiary, claim account ownership, or approve a payment solely because this calculator returned a mathematically valid string.

Official IBAN Format References

Use current official specifications when national formats or production validation rules matter.

• Swift IBAN Registry — The registration authority’s current national IBAN format registry.
• ISO 13616-1 — The international standard defining the elements of an IBAN.