US Routing Number (ABA) Validator
Enter a US bank routing number to check that it is nine digits and passes the ABA checksum. If it is valid, the tool shows the Federal Reserve region its leading digits point to. This checks the number's form, not whether the bank is real.
Processed entirely in your browser. This validator runs on your device using JavaScript. The number you enter is never sent to a server, stored, or logged, and nothing leaves your device.
How It Works
A US bank routing number is nine digits, and the last digit is a check digit calculated from the other eight. That built-in relationship is what lets a payment form reject a mistyped number without contacting the bank. The first two digits also fall in set ranges tied to the Federal Reserve, which the tool reads to report a region.
The checksum weights the digits in a repeating pattern of 3, 7, and 1, then checks that the total is a multiple of ten. Writing the nine digits as d1 through d9, the rule is:
| Group | Digits | Weight |
|---|---|---|
| 1 | d1, d4, d7 | times 3 |
| 2 | d2, d5, d8 | times 7 |
| 3 | d3, d6, d9 | times 1 |
Add the three weighted groups together, and the number is valid when that total divides evenly by ten.
Worked Example
Take the sample number 123456780, which is made up rather than a real bank's. The first group is 3 times (1 plus 4 plus 7), which is 36. The second is 7 times (2 plus 5 plus 8), which is 105. The third is (3 plus 6 plus 0), which is 9. Adding them gives 150, a multiple of ten, so the number passes the ABA checksum.
When You Would Use This
Setting up a direct deposit, a bill payment, or a wire transfer means entering a routing number, and a single wrong digit can misdirect or bounce the payment. A quick checksum check catches that before it causes a problem. Because it is a US payment number, it pairs naturally with the credit card validator, which uses a similar check-digit idea.
Frequently Asked Questions
Does a valid result mean the bank is real?
No. A pass means the nine digits are internally consistent under the ABA checksum, which is how a form catches a mistyped number. It does not confirm the number belongs to an open, active bank. Your own bank or the ABA registry can confirm that.
What is a routing number?
It is a nine-digit code that identifies a US bank or credit union in payments such as direct deposits, wire transfers, and cheques. It is sometimes called an ABA number, after the American Bankers Association, which introduced the system.
What is the difference between a routing number and an account number?
The routing number identifies the bank; the account number identifies your specific account at that bank. On a paper cheque, the routing number is the first group of nine digits along the bottom, and the account number follows it.
Why do routing numbers have a check digit?
The last digit is calculated from the other eight so the weighted sum lands on a multiple of ten. It exists to catch single wrong digits and most swapped pairs before a payment is submitted, not to prove the bank exists.
Is my routing number sent anywhere?
No. The check runs entirely in your browser. Nothing you type is transmitted, stored, or logged.