What an IBAN Is
An IBAN — International Bank Account Number — is the globally standardized format for bank accounts. It combines a 2-letter country code, 2 check digits, and the country's existing local account number (BBAN — Basic Bank Account Number). Total length varies by country: 16 characters in Belgium, 22 in the UK, 24 in Spain, 27 in France, 31 in Malta. About 75 countries issue IBANs — every EU/EEA country, the UK, Switzerland, most of the Middle East, and a growing list elsewhere.
The point of IBAN is interoperability: a single string the sender can check and the receiving bank can route, regardless of country. The IBAN Validator checks any candidate IBAN against the ISO 13616 standard's three rules — valid country, correct length for that country, and a passing mod-97 checksum.
How the Microapp IBAN Validator Works
Type or paste the IBAN. The result appears instantly. Whitespace and case are normalized — de89 3704 0044 0532 0130 00 and DE89370400440532013000 validate identically. Two sample buttons are included: a real test IBAN that validates, and the same IBAN with the last two digits tweaked so it fails the checksum (good for seeing what the error message looks like).
Three checks run in sequence: (1) Is the country code one that issues IBANs? (2) Does the length match what that country uses? (3) Does the mod-97 checksum on the rearranged number equal 1? All three must pass for the IBAN to be valid.
DE89 3704 0044 0532 0130 00 (the official ISO test IBAN, Deutsche Bank).Step 1: country DE → German IBANs exist ✓
Step 2: length 22 → matches Germany's 22-char format ✓
Step 3: rearrange to
3704004405320130 00DE89, replace letters with numbers (D=13, E=14), compute mod 97 → result is 1 ✓Result: ✓ Valid IBAN. Germany · 22 characters.
Why the US Doesn't Use IBANs
The United States uses a different system entirely: ABA routing number (9 digits identifying the bank) plus account number (variable length, identifying the account at that bank). When a US wire transfer comes in via SWIFT, the message uses routing + account, not an IBAN. Banks have never converted because the existing system works domestically and SWIFT handles cross-border routing without needing IBANs.
If a tool gives you a "US IBAN", it's something a third-party invented (or a bug). Banks can't issue real IBANs for US accounts. Same for Canada, Japan, China, India, and most of Asia — IBAN coverage is mostly Europe + Middle East.
What the Mod-97 Checksum Catches
The two-digit check digits at positions 3-4 of an IBAN are computed so that, when you move the first 4 characters to the end and replace each letter with its position-9 numeric value (A=10, B=11, ..., Z=35), the resulting big number has a remainder of exactly 1 when divided by 97. The math comes from a 1997 paper proving that mod-97 catches:
- All single-digit typos (1 → 7, etc.) — 100% catch rate
- All single transpositions of adjacent digits (12 → 21) — 100%
- Most double errors and many transpositions of non-adjacent digits
Same idea as the Luhn algorithm in credit cards (mod 10 with weights), but with stronger detection because 97 is prime. The catch rate isn't 100% for every error type, but it's high enough that IBANs typed by humans rarely pass the check accidentally.
Length Per Country
| Country | Code | Length | Country | Code | Length |
|---|---|---|---|---|---|
| Germany | DE | 22 | UK | GB | 22 |
| France | FR | 27 | Italy | IT | 27 |
| Spain | ES | 24 | Netherlands | NL | 18 |
| Belgium | BE | 16 | Switzerland | CH | 21 |
| Sweden | SE | 24 | Poland | PL | 28 |
| Norway | NO | 15 | Malta | MT | 31 |
Norway's 15-character IBAN is the shortest; Malta's 31 is the longest. Each country's length is fixed — there's no "short form" or "long form" within a country.
What a Valid IBAN Doesn't Tell You
Whether the account exists. The validator confirms structural correctness — country + length + checksum. It can't tell you whether the bank has actually issued that specific number to a real customer. For that, you need a payment provider's account-name match service (most banks expose one for SEPA payments).
Whether the account is active. A previously-valid IBAN remains structurally valid even after the account is closed. The bank's records know the account is closed; the IBAN string itself doesn't.
Whose account it is. IBAN doesn't carry a name. The bank does the name-account match check during the transfer; you can't validate "is this John Doe's account?" from the IBAN alone.
Common Pitfalls
Treating IBAN as secret. IBANs aren't secret — they're like phone numbers for bank accounts. Sharing your IBAN is normal (it's how people pay you). The risk is reading: someone with your IBAN can't withdraw money from it, but they could initiate a SEPA direct debit if your bank doesn't require additional authorization. SEPA debits can be reversed within 8 weeks; the risk is real but bounded.
Confusing IBAN with SWIFT/BIC. Different things. SWIFT/BIC identifies the bank (e.g. DEUTDEFF = Deutsche Bank Frankfurt). IBAN identifies the account (e.g. DE89 3704 ...). Cross-border transfers usually need both. Within SEPA (Europe), the IBAN alone is enough since 2016.
Pasting from a PDF with smart quotes or non-ASCII spaces. Some PDFs replace regular spaces with non-breaking spaces (U+00A0) or other invisible characters. The validator strips them, but if validation still fails, copy the IBAN into a plain text editor first to see what's actually there.
Related Tools
For credit-card-payoff calculations (separate financial concern), see the Credit Card Payoff Calculator. For generating UUIDs for transaction references, the UUID Generator is the right tool. To convert numbers to words for written checks, see Number to Words. For unit conversion in international finance contexts (currencies aren't included, but lengths and weights are), the Unit Converter handles physical units.