ABA Routing Number Validator

About this calculator

A U.S. ABA routing number (also called an RTN) is a 9-digit code identifying the financial institution on a check or ACH transfer, where the ninth digit is a checksum computed from the first eight: 3(d1+d4+d7) + 7(d2+d5+d8) + (d3+d6+d9) must be evenly divisible by 10 for the number to be structurally valid. The formula was designed by the American Bankers Association in 1910 to let clearinghouses catch transcription errors before a payment is misrouted.

This validator runs the checksum on a 9-digit number you enter and reports whether it passes, without confirming the routing number is actually assigned to a real bank (that requires a lookup against the Fed's registry). Developers building payment or ACH integrations, and bookkeepers double-checking a check use it as a fast first-pass sanity check before submitting a transaction or entering banking details into a form.