IBAN Validator
An IBAN (International Bank Account Number) embeds the country, two check digits, and a country-specific BBAN. Validation is two steps: (1) length matches the country's published spec, (2) the mod-97 checksum is 1 after rearranging and converting letters to digits. This tool runs both checks locally and shows the parsed country, check digits, BBAN, and any errors. Useful for spotting typos in payment forms before sending money.
Paste an IBAN above to validate.
Validation is local (no network calls). Checksum proves the IBAN is well-formed, not that the account actually exists.
How to use
- Paste an IBAN. Spaces and case don't matter — they get normalized.
- Read the status: ✓ valid means length + checksum both passed.
- If invalid, the error list pinpoints what's wrong (bad character, wrong length, failed checksum, unknown country).
Frequently asked questions
- Does a valid IBAN mean the account exists?
- No. The checksum only catches typos and transcription errors. A real bank-account-existence check requires the bank's API (e.g. SEPA SCT Inst lookup) — we can't do that from the browser.
- Why does my US/Canadian account fail?
- The US, Canada, Australia, NZ, and most non-European countries don't use IBAN. They use ABA/routing + account number or local schemes. IBAN is mostly Europe, the Middle East, and parts of the Caribbean.
- How is the mod-97 check computed?
- Move the first 4 chars (country + check digits) to the end, replace each letter with its A=10, B=11, ..., Z=35 numeric value, and compute the resulting big number mod 97. A valid IBAN gives 1.
- Are check digits the same as account check digits?
- No — IBAN check digits are computed from the BBAN. The BBAN itself may have its own internal check digits (e.g. Spain has two), which are separate.
Related tools
Credit Card Validator (Luhn + Brand)
Validate a card number with the Luhn checksum, detect brand (Visa/MC/Amex/etc), and check expected length. Local, no network.
Modular Exponentiation Calculator (aᵇ mod m)
Compute a^b mod m exactly for arbitrarily large integers using fast binary exponentiation, plus the modular multiplicative inverse of the base. Ideal for RSA, Diffie-Hellman and number-theory work.
ISBN Validator (ISBN-10 / ISBN-13)
Validate ISBN-10 and ISBN-13 checksums and convert between the two formats. Hyphens and spaces are handled.
Fibonacci Sequence Generator
Generate the first N Fibonacci numbers — 0, 1, 1, 2, 3, 5, 8 … — with exact big-integer precision, and see the last term, the running sum and the golden-ratio approximation of the final two terms.
Number Formatter (Intl.NumberFormat)
Format a number the way each locale expects — `1,234,567.89`, `1.234.567,89`, `$1.23M`, `12 345 ₽` — and grab the matching JavaScript snippet.
Fraction Calculator — Add, Subtract, Multiply, Divide
Add, subtract, multiply, and divide fractions, mixed numbers, and decimals. Get the reduced fraction, mixed number, decimal, and worked steps.