What is a French IBAN and how long is it?

A French IBAN (International Bank Account Number) is always exactly 27 characters long. It starts with the country code FR, followed by 2 ISO check digits, then a 23-character BBAN made up of a 5-digit bank code (code banque), a 5-digit branch code (code guichet), an 11-character account number, and a 2-digit RIB key (clé RIB). Example format — FR76 3000 6000 0112 3456 7890 189.

What is the RIB key (clé RIB) and how is it calculated?

The RIB key is a 2-digit national check digit appended to French bank account numbers before they were replaced by IBANs. It is calculated using a weighted sum over the bank code, branch code and account number with weights 89, 15 and 3 respectively, using a French alphanumeric mapping where A-I map to 1-9, J-R map to 1-9 again, and S-Z map to 2-9. The formula is (97 minus ((89 times bank plus 15 times branch plus 3 times account) mod 97)). A valid RIB key proves the three fields form a consistent French account reference.

How does the ISO 7064 mod-97 IBAN checksum work?

The four leading characters (FR and the two check digits) are moved to the end of the string. Each letter is replaced by two digits using A=10 through Z=35. The resulting long number is divided by 97 and the remainder must equal exactly 1. This tool folds the modulus progressively digit by digit so no large integers are needed. A pass confirms the IBAN is internally consistent; it does not confirm the account is open.

Can an IBAN pass mod-97 but still be wrong?

Yes. The mod-97 check guards against most single-digit typos and transposition errors but it is not cryptographic. A completely fabricated number could pass by chance (roughly 1 in 97 random IBANs of the right length pass). The RIB key provides a second independent layer of verification specific to French accounts. Only your bank can confirm the account truly exists.

What do the fields in a French IBAN mean?

The 23-character BBAN breaks down as follows. The first 5 digits are the code banque identifying the financial institution (e.g. 30006 is BNP Paribas). The next 5 digits are the code guichet identifying the specific branch. The following 11 characters are the account number proper, which may include letters in older accounts. The final 2 digits are the clé RIB, a checksum over the three preceding fields that was part of the original French RIB format before IBAN adoption.

Is my IBAN sent to a server?

No. Every calculation — the RIB key formula and the ISO 7064 mod-97 — runs entirely in your browser using JavaScript. Your IBAN is never transmitted, logged, or stored anywhere. You can disconnect from the internet and the tool will still work.

French IBAN Validator

A French IBAN carries more built-in error-detection than most other countries’ IBANs because it layers two independent checksums on top of each other: the universal ISO 7064 MOD-97-10 checksum shared by all IBANs worldwide, plus a France-specific RIB key (clé RIB) that was part of the original French bank account format long before IBAN adoption. This tool runs both checks instantly in your browser, decodes every structural field, and explains exactly what each part of the number means — useful whether you are onboarding a French supplier, validating input in a payments system, or just checking that your own bank details are correct before sharing them internationally.

French IBANs appear in everyday banking contexts including SEPA credit transfers, SEPA direct debits, salary mandates, invoice payment instructions, and online checkout forms for French merchants. The format has been mandatory for cross-border euro payments since 2008, and most French banks now display it on debit cards and statements alongside the older RIB slip format.

How it works

A French IBAN is always 27 characters long and follows this structure:

FR + kk + bbbbb + ggggg + aaaaaaaaaaa + cc

where FR is the country code, kk is the two-digit IBAN check field, bbbbb is the 5-digit bank code (code banque), ggggg is the 5-digit branch code (code guichet), aaaaaaaaaaa is the 11-character account number, and cc is the 2-digit RIB key (clé RIB).

Step 1 — RIB key check. The clé RIB is computed by mapping each character to a digit using the French alphanumeric table (A–I = 1–9, J–R = 1–9, S–Z = 2–9), then applying the weighted formula 97 - ((89 * bank + 15 * branch + 3 * account) mod 97). The two digits at the end of the BBAN must equal this expected value.

Step 2 — ISO 7064 MOD-97-10 checksum. The first four characters are moved to the end. Each letter is replaced with two digits using the standard IBAN table (A=10, Z=35). The entire number is divided progressively by 97; the remainder must be exactly 1.

Both steps run locally — nothing is ever sent over the network.

Worked example

Take the test IBAN FR76 3000 6000 0112 3456 7890 189:

Country: FR, check digits: 76
Bank code: 30006 (BNP Paribas), branch code: 00001
Account number: 12345678901
RIB key: 89

RIB check: (89 * 30006 + 15 * 00001 + 3 * 12345678901) mod 97 = 8 then 97 - 8 = 89. The stored key 89 matches, so the RIB is valid.

MOD-97 check: rearrange to 300060000112345678901897 6FR76, expand letters F=15, R=27 to get a long digit string, compute mod 97 — result is 1, so the IBAN checksum also passes.

Field	Value	Length
Country code	FR	2
IBAN check digits	76	2
Bank code (code banque)	30006	5
Branch code (code guichet)	00001	5
Account number	12345678901	11
RIB key (clé RIB)	89	2
Total		27

Both checks passed. The IBAN is structurally valid for France. Whether the account is actually open is only known to the bank.