ABA Routing Number Validator
Validate a 9-digit US ABA routing transit number using its position-weighted checksum.
Enter a value above to validate it instantly.
US bank routing numbers are 9 digits with a checksum: 3·(d1+d4+d7) + 7·(d2+d5+d8) + (d3+d6+d9) must be divisible by 10. This tool runs that calculation and tells you whether a number is structurally valid.
A valid checksum means the number is well-formed, not that it maps to an active bank or account. Use it to test ACH and banking form validation with confidence.
Frequently asked questions
Does a valid routing number identify a real bank?+
The checksum only confirms the number is well-formed. Mapping a routing number to a specific bank requires a separate directory lookup.