Routing Number Validator

How to use

1. 1Choose Single number for a full breakdown of one routing number, or Batch list to check one routing number per line.
2. 2Type or paste the routing number. It is reduced to digits automatically, so the printed form with spaces or dashes works as is.
3. 3Read the verdict and the per-check details: the 9-digit length, the 3-7-1 mod 10 checksum, and the Federal Reserve routing symbol prefix.
4. 4If the check digit is wrong, the result shows the digit it should be and the corrected number, so a single typo is easy to spot and copy.
5. 5In batch mode, read the per-row status and counts, then use Copy valid only to keep just the routing numbers that pass.

About this tool

Routing Number Validator checks United States ABA routing transit numbers entirely in your browser, using only the two properties of a routing number that are deterministic and publicly documented, so there is no lookup against any external database. The first property is the check digit. A routing number is exactly nine digits, and the ninth digit is a checksum over the first eight using the classic 3-7-1 weighting: multiply the nine digits by the repeating weights 3, 7, 1, add the products, and a valid routing number's total is divisible by 10. Because the check digit is fully determined by the first eight digits, the tool can also tell you the digit that should have been there when a number fails, and it shows the corrected nine-digit number so you can spot a single mistyped digit immediately. The second property is the routing symbol prefix. The first two digits encode which Federal Reserve district processes the institution and what type of institution it is: 01 to 12 are primary routing symbols for the twelve Federal Reserve districts from Boston through San Francisco, 21 to 32 are the same districts for thrift institutions, 61 to 72 are the same districts for electronic transactions such as ACH, 00 is reserved for United States Government and federal institutions, and 80 is a reserved test prefix. The breakdown panel splits the number into its three documented parts, the Federal Reserve routing symbol (digits one to four), the ABA institution identifier (digits five to eight), and the check digit (digit nine), and names the district and city for the prefix. Because a number like 000000000 can pass the raw checksum while belonging to no assigned prefix block, the overall verdict requires both a passing checksum and a recognized prefix, which prevents false positives that a checksum-only checker would report as valid. Single mode gives the full breakdown for one number, with copy buttons for the number and for the corrected number when the check digit is wrong. Batch mode validates an entire column at once, one routing number per line, cleans each line down to its digits so spaces and dashes in printed forms do not matter, marks every row valid, invalid, or skipped with a short reason, counts the totals, and lets you copy back only the valid entries, which is the fastest way to clean a list of routing numbers from a spreadsheet, a vendor file, or a customer onboarding export. This tool is useful for QA on bank transfer and direct deposit forms, validating ACH and wire details before a payment run, cleaning supplier and payroll records, and catching transcription errors in routing numbers copied from checks or statements. A passing result proves only that the number is well formed. It does not prove that a bank or an account exists, and it does not identify the current owning institution, which can only be confirmed in the Federal Reserve E-Payments Routing Directory. Everything is computed locally on your device, so the routing numbers you paste here are never uploaded, logged, or sent anywhere.

Free to use. Works in your browser. No signup, no login.