ABA Routing Number Validator US
Check a 9-digit US routing number — check digit, Federal Reserve district and structure — instantly in your browser, nothing sent to a server.
What is an ABA routing number?
An ABA routing number (also called a routing transit number, or RTN) is the 9-digit code that identifies a bank or credit union in the United States for ACH transfers, wires and checks. Its last digit is a check digit computed with the ABA 3-7-1 weighting, so typos can be caught. This free tool verifies that check digit and decodes the Federal Reserve routing symbol entirely in your browser — nothing is uploaded.
About the ABA routing number validator
A routing number (ABA RTN) has nine digits: the first four are the Federal Reserve routing symbol, the next four identify the financial institution, and the ninth is a check digit. On a US check or ACH payment it sits next to the account number to say which bank holds the account.
ValidateFin checks the number locally in your browser: it confirms the 9-digit length, validates the check digit with the ABA 3-7-1 mod-10 algorithm, and reads the first two digits to show the Federal Reserve district and how the number is used (primary, thrift, electronic/ACH, government or traveler's cheque). No routing number is ever sent to a server. A valid check digit means the number is well-formed — it does not by itself prove the bank is currently active, which requires the official Federal Reserve / Accuity directory.
Key facts about ABA routing numbers
- A routing number is exactly 9 digits: a 4-digit Federal Reserve symbol, a 4-digit institution identifier and 1 check digit.
- The check digit uses the ABA 3-7-1 weighting: the weighted sum of all nine digits must be a multiple of 10.
- The first two digits map to a Federal Reserve district (01-12), with thrift (21-32) and electronic (61-72) ranges.
- A routing number identifies the bank; the account number identifies the account — both appear on a US check.
- A valid check digit catches typos and transposed digits, but does not guarantee the bank is still active.
Frequently asked questions
What is an ABA routing number?
It is the 9-digit code (routing transit number) that identifies a US bank or credit union for ACH transfers, wire transfers and checks. It was created by the American Bankers Association, hence "ABA".
How is a routing number validated?
The nine digits are weighted 3, 7, 1 repeating; the weighted sum must be a multiple of 10. The ninth digit (the check digit) is chosen to make that true, so a single typo or transposition breaks the check.
What do the parts of a routing number mean?
The first four digits are the Federal Reserve routing symbol (which district and office), the next four identify the specific bank, and the last digit is the check digit.
Is my routing number uploaded anywhere?
No. The number is validated entirely in your browser with JavaScript. Nothing is ever sent to a server.
Does a valid routing number mean the bank exists?
A valid check digit confirms the number is well-formed and could be a real routing number, but it does not confirm the bank is currently active. Only the official Federal Reserve / Accuity directory does that.
What is the difference between a routing number and an IBAN?
A routing number identifies a US bank and is used with a separate account number, while an IBAN is the international format used across Europe and beyond that embeds the country, bank and account in one string. ValidateFin has a dedicated IBAN validator too.