What is the format of a German IBAN?

A German IBAN is always exactly 22 characters: the two-letter country code DE, two check digits, an 8-digit Bankleitzahl (BLZ, bank sort code), and a 10-digit Kontonummer (account number). The full BBAN (positions 5 to 22) contains only digits — no letters appear after the country code.

How does ISO 7064 MOD-97-10 validation work?

The algorithm rearranges the IBAN by moving the first four characters (country code plus check digits) to the end, then converts every letter to its two-digit numeric equivalent (A=10, B=11, ... Z=35). The resulting number is divided by 97 using progressive folding to avoid overflow. A valid IBAN produces a remainder of exactly 1.

What is a Bankleitzahl (BLZ) and what does the first digit mean?

The Bankleitzahl is the 8-digit German bank sort code that identifies the paying bank. The first digit is the Clearingbereich (clearing area) and encodes the region of Germany — digit 1 is Berlin/East Germany, 2 is Hamburg/north, 3 is Lower Saxony/Bremen, 4 and 5 are North Rhine-Westphalia, 6 is Hesse/Rhine-Palatinate, 7 is Bavaria/Baden-Württemberg, 8 is Saxony/Thuringia, and 9 is Franconia/Northern Bavaria. A BLZ can never start with 0.

What is a Kontonummer?

The Kontonummer is the 10-digit account number within the bank identified by the BLZ. Together the BLZ and Kontonummer uniquely identify a German bank account. Before SEPA, these were the primary payment identifiers in Germany; they are now embedded inside the IBAN.

Does a valid result mean the account exists?

No. A pass means the IBAN is structurally and mathematically well-formed according to the SWIFT IBAN registry and ISO 7064. It cannot confirm the account is open, funded, or belongs to any specific person. Only the bank holding the account can verify that.

Is this tool compliant with the SWIFT IBAN Registry?

Yes. The German IBAN specification (DE, 22 characters, 8-digit BLZ plus 10-digit Kontonummer) is taken directly from the SWIFT IBAN Registry. The MOD-97-10 checksum algorithm matches ISO 13616 exactly. The tool implements only what the registry documents.

German IBAN Validator

The German IBAN Validator checks whether a German bank account number in IBAN format is structurally correct. It verifies the country code, the total 22-character length, the Bankleitzahl (BLZ) clearing-area digit, the Kontonummer format, and the full ISO 7064 MOD-97-10 checksum — all without sending a single character to a server.

German IBANs became mandatory for domestic payments on 1 February 2014 under the SEPA migration, replacing the older BLZ + Kontonummer pair. Today, every wire transfer, direct debit mandate, and payroll run in Germany requires a valid IBAN, which makes a fast, offline validator useful for catching typos in HR systems, accounting imports, and form validation.

How it works

A German IBAN has a precisely defined structure laid out in the SWIFT IBAN Registry:

DE — the ISO 3166-1 alpha-2 country code for Germany (always uppercase)
kk — 2 check digits computed by the ISO 7064 MOD-97-10 algorithm
bbbbbbbb — the 8-digit Bankleitzahl (BLZ), where the first digit encodes one of nine clearing areas (1 = Berlin/East Germany through 9 = Northern Bavaria)
cccccccccc — the 10-digit Kontonummer (account number at the named bank)

Total: 22 characters, all alphanumeric, with only digits in the BBAN section (positions 5–22).

The checksum calculation follows ISO 13616 / ISO 7064 MOD-97-10 exactly:

Strip spaces and convert to uppercase.
Move the first four characters (DE + check digits) to the end.
Replace each letter with its 2-digit numeric code: D = 13, E = 14, giving 1314 for DE.
Interpret the resulting string as an integer and compute the remainder when divided by 97, folding progressively to avoid overflow.
The IBAN is valid if and only if the remainder equals 1.

The tool also extracts and labels the BLZ and Kontonummer so you can confirm the right bank-region is encoded.

Worked example

Take the IBAN DE44 5001 0517 5407 3249 31:

Country code: DE — Germany
Check digits: 44
BLZ: 50010517 — first digit 5 maps to the North Rhine-Westphalia (south) / Cologne / Dusseldorf clearing area
Kontonummer: 5407324931

To verify the checksum, move DE44 to the end and expand the letters:

50010517540732493113 1444

Fold this over mod 97: the remainder is 1, so the IBAN is valid.

Field	Value	Meaning
Country	DE	Germany
Check digits	44	MOD-97 checksum pair
BLZ	50010517	Commerzbank Frankfurt (clearing area 5)
Kontonummer	5407324931	Account at that bank
Total length	22	Matches the SWIFT registry

Changing any single digit in a valid IBAN almost always produces a remainder other than 1, which is why the checksum catches most typos.

Every character is processed locally — nothing is uploaded, logged, or transmitted.