Routing number validator
Check whether a 9-digit US routing number passes the ABA checksum. A pass means the format is right, not that the bank is active.
Input
Routing number check
—Enter a 9-digit ABA routing number to verify its checksum.
- Length
- 9 digits
- Standard
- ABA
Related tools
Guides
This routing number validator runs the two checks a payment form should run before accepting a US ABA routing number. The first two digits have to fall in a prefix range the routing system uses, and the 3-7-1 weighted checksum has to come out to a multiple of 10. A pass tells you the number is well formed. It doesn't tell you the bank exists, is still open, or holds the account you're about to pay. The check runs in your browser, and the number you type isn't sent anywhere.
How to validate a routing number
- Type or paste the number. Spaces, dashes, and other non-digit characters are ignored.
- If there aren't exactly 9 digits, the tool tells you how many it found.
- With 9 digits, it checks the prefix and the checksum, then shows either Valid ABA routing number or Invalid, checksum failed. An out-of-range prefix gets the same Invalid message.
- A valid number is split into its routing symbol (first four digits), institution identifier (next four), and check digit.
- The example buttons load a known valid number (Chase or Bank of America) and an invalid one.
The ABA 3-7-1 weighted checksum explained
Each digit is multiplied by a weight from the repeating pattern 3, 7, 1, so positions 1 to 9 get 3, 7, 1, 3, 7, 1, 3, 7, 1. Add up the nine products. For a valid routing number the total is a multiple of 10. Chase's 021000021 gives 0 + 14 + 1 + 0 + 0 + 0 + 0 + 14 + 1 = 30, so it passes.
The weights are chosen so that any single mistyped digit changes the total and fails the check. Swapping two adjacent digits is caught too, unless the two digits differ by exactly 5 (a 2 and a 7, say). The tool also rejects numbers whose first two digits fall outside 00 to 12, 21 to 32, 61 to 72, or 80, as well as 000000000.
What checksum validation does not confirm
- Whether the routing number belongs to a real, currently active financial institution.
- Whether the bank accepts ACH, wires, or other specific transfer types.
- Whether the account number paired with this routing number is valid.
- Whether the number is still in use. Banks merge and retire routing numbers, and an old one still passes the checksum.
Frequently asked questions
What does routing number validation check?
That the number has 9 digits, starts with a prefix the routing system uses, and passes the ABA 3-7-1 checksum. It doesn't look the number up in the Federal Reserve's directory.
How do I know if a routing number belongs to a real bank?
Look it up in the Federal Reserve's E-Payments Routing Directory on frbservices.org, or check your bank's website or a printed check. Those sources show whether the number is active.
Why does routing number validation matter?
It catches typos before a payment goes out. Every single-digit mistake fails the checksum, so a mistyped number gets flagged before it turns into a returned ACH payment.
Does this tool store the routing numbers I enter?
No. Validation runs in your browser, and the number you type isn't sent to a server or a third party.
Built and maintained by Bipul Kumar. Found a wrong number or a broken result? Tell me and I'll fix it.