Free tool
Czech account number to IBAN and back
Type a Czech account number with its bank code (e.g. 19-2000145399/0800) and see the IBAN, bank and BIC at once; an IBAN gives you the account number back. The tool checks the check digits, so it catches a typo in the number. Paste many accounts one per line and download them as CSV. Free, and nothing is sent anywhere.
Convert an account number or IBAN
At most 1,000 lines.
Nothing is sent anywhere: the conversion and check run only in your browser.
3 steps
How it works
Type the account or IBAN
An account number with or without its prefix and the bank code after a slash, or an IBAN with or without spaces.
Check the result
You see the account number, IBAN, bank and BIC, and whether the check digits hold.
In bulk to CSV
Paste several accounts one per line; download the result as CSV for Excel.
Good to know
- Nothing is sent to any server and nothing is stored.
- The check covers the shape of the number and its check digits (modulo 11 under the Czech National Bank's decree, modulo 97 for an IBAN). It does not check that the account exists or whose it is.
- Banks and BICs come from the Czech National Bank's list of bank codes (downloaded on 3 November 2026).
- A foreign IBAN is checked, but it cannot become a Czech account number.
Frequently asked questions
Short answers on this topic.
Are the account numbers sent anywhere?
No. The conversion and the check run right in your browser. Nothing goes to Zettl's server or anywhere else, and nothing is stored.
How is a Czech IBAN made?
CZ, two check digits, the four-digit bank code, the six-digit prefix and the ten-digit account number, both padded with zeros on the left. The check digits are computed with modulo 97.
Why does it say my account number is not valid?
A Czech account number has a checksum (modulo 11). When it fails, there is most likely a typo or swapped digits. Check the bank code after the slash too.
Does the tool cost anything, or do I need an account?
No. The tool is free and needs no sign-up.
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