Validate US bank routing numbers (ABA/RTN) and check their authenticity.
A routing number, also known as an ABA (American Bankers Association) routing transit number (RTN), is a nine-digit code used to identify a financial institution in the United States for the purpose of transferring money.
| Digits | Purpose |
|---|---|
| 1-2 | Federal Reserve routing symbol |
| 3-4 | ABA institution identifier |
| 5-8 | Specific institution code |
| 9 | Check digit (validation) |
Routing numbers use a checksum formula for validation:
3(d1 + d4 + d7) + 7(d2 + d5 + d8) + (d3 + d6 + d9) mod 10 = 0