ABA Routing Number Validator
Verify US bank routing numbers with the official checksum and decode the district range.
Validate US ABA routing numbers instantly. Free routing number checker with 3-7-1 checksum and Federal Reserve district decode.
Calculator Inputs
About Routing Check
Verify US bank routing numbers with the official checksum and decode the district range.
Nine digits weighted 3-7-1 repeating must sum to a multiple of 10. The first two digits also reveal the class: 01–12 are Federal Reserve districts, 21–32 thrifts, 61–72 electronic processing.
A passing checksum proves structure, not that the account exists or the bank honors it — confirm details with the institution for real transfers. Everything runs in your browser.
Where it is used
Checking direct-deposit details, validating payment forms, and catching typos before failed transfers.
How to use the Routing Check
- Routing Number (9 digits) — enter the value (e.g. 021000021).
- Calculate — press the Calculate button to see the result instantly above.
Formula
(3×(d1+d4+d7) + 7×(d2+d5+d8) + (d3+d6+d9)) mod 10 = 0.
Examples
Example
Frequently Asked Questions
- Why do checks and wires use different numbers?
- Many banks issue separate ABA numbers per channel (paper, wire, ACH). Always use the one matching your transfer type.
- Does valid mean the account exists?
- No — only that the routing number is well-formed and its district decodes. Account existence needs the bank.
- What is the 3-7-1 weighting for?
- It catches single-digit errors and most transpositions — the two typo classes that cause misdirected payments.