US ABA Routing Number Validator
Validate a US bank routing number's checksum and identify the Federal Reserve region.
Overview
A US ABA routing number is the nine-digit identifier used to route domestic ACH transfers, wire transfers, and paper checks to the correct US bank. The American Bankers Association introduced the numbering scheme in 1910 and the Federal Reserve maintains it today. A valid routing number satisfies a position-weighted checksum and its first two digits map to a specific Federal Reserve district. A validator confirms both — useful before posting payment instructions to a partner or printing on a check.
The routing number alone does not identify a specific account, only the institution. It pairs with the account number to form the routing-account pair used in payment messages. Some banks publish separate routing numbers for ACH versus wire versus paper-check use; the validator checks the format and checksum but cannot determine which transaction type the number is licensed for. Routing numbers also do not encode the branch beyond the city or region historically associated with the issuing Federal Reserve office.
How it works
The checksum, defined in Federal Reserve operating rules, applies position weights 3, 7, 1, 3, 7, 1, 3, 7, 1 to the nine digits and verifies that the weighted sum modulo 10 equals zero. The first two digits indicate the Federal Reserve district: 00 is special (US Government), 01–12 map to the twelve Reserve districts (Boston, New York, Philadelphia, Cleveland, Richmond, Atlanta, Chicago, St. Louis, Minneapolis, Kansas City, Dallas, San Francisco), and 21–32 are thrift institutions. Digits in the range 61–72 denote electronic transactions; 80 indicates traveler's checks. Outside these ranges, the number is invalid.
Examples
011000015— Federal Reserve Bank of Boston (district01). Weighted sum(0×3 + 1×7 + 1×1 + 0×3 + 0×7 + 0×1 + 0×3 + 1×7 + 5×1) = 20. 20 mod 10 = 0. Valid.021000021— JPMorgan Chase, district02(New York). Valid checksum.121000358— Bank of America, district12(San Francisco). Valid.091000019— Wells Fargo Minneapolis (district09). Valid.111111111— fails the weighted-sum check; the digits sum to 11, which is non-zero modulo 10.
FAQ
Is the routing number on a check public?
Yes — by design. The risk is on the paired account number, which combined with the routing number can be used to attempt an ACH debit.
Why do banks have multiple routing numbers?
Mergers and historical regional offices leave legacy numbers in use; some institutions also separate by transaction type (paper, ACH, wire).
Does ABA validation work for Canadian banks?
No. Canada uses a separate institution and transit number scheme.
Can the checksum tell me the bank's name?
No — only the Federal Reserve district. Mapping to a specific institution requires the FedACH directory or FRB participant file.
Are routing numbers reused after a bank closes?
Generally not for a long retirement period; the Fed retires the number to avoid collisions with cleared items.