ABA Routing Number Validator
Validate a US bank routing number's format and ABA checksum in your browser. A first-line check for onboarding and payment forms. Nothing is sent.
Everything runs in your browser. No data is uploaded or stored.
About this tool
Straightforward and private: A validator for US ABA routing numbers that checks the 9-digit format and the official ABA checksum.
The routing number carries a weighted check digit, so a single mistyped or transposed digit fails the test — the same first-line check payment and onboarding systems use before contacting a bank. The arithmetic runs in your browser.
It confirms a number is well-formed, not that the bank or account is real.
How to use it
- Enter the 9-digit routing number.
- Read whether the length and ABA checksum pass.
- If it fails, re-check the digits — most failures are one wrong character.
Frequently asked questions
Does passing mean the account is valid?
No. It means the routing number is correctly formed. Whether the bank and account exist requires a bank-level check, not a checksum.
Is the number stored?
No. It is validated locally and never transmitted.
What does the ABA checksum check?
It applies weights 3, 7, 1 across the nine digits and requires the weighted sum to be divisible by 10. That catches the common typo and transposition errors.