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ABA routing number validator
Instantly check the 9-digit format, the ABA mod-10 checksum and the Federal Reserve routing prefix of any US routing number. No sign-up, and nothing is sent anywhere.
This tool validates the 9-digit ABA format, checksum and routing prefix only. It does not confirm the bank, the branch, or that an account exists.
Step by step
How to validate an ABA routing number
It takes a few seconds and happens entirely on your device.
Enter the routing number
Type or paste the 9-digit US routing number into the field. Spaces and dashes are ignored.
Run the check
Select Validate. The tool checks the length, digits, ABA mod-10 checksum and Federal Reserve routing prefix — all in your browser.
Read the result
See whether the checksum passes and view the prefix, Federal Reserve routing and check digit breakdown.
Anatomy
What is an ABA routing number?
An ABA routing number (routing transit number) identifies a US bank or credit union in ACH transfers, wires and checks. It is exactly nine digits in three parts: a four-digit Federal Reserve routing symbol, a four-digit institution identifier, and a final check digit. Using the example 0210 0002 1:
Under the hood
How the ABA checksum works
Every routing number ends in a check digit that has to satisfy a fixed weighted formula — that is what catches typos before a payment is ever submitted.
Exactly 9 digits
A routing number is always nine digits, 0–9 only. The tool strips spaces and dashes, then confirms the length and that every character is a digit.
The mod-10 checksum
Label the digits d1 through d9. The weights (3, 7, 1) repeat across the positions, and the weighted sum must be a multiple of 10. A single mistyped digit — or two digits swapped — almost always breaks it.
What it can and can't do
The checksum and prefix check catch most keying errors. They cannot confirm the bank, the branch, or that an account exists — always confirm details with the recipient or the bank.
3×(d1 + d4 + d7) + 7×(d2 + d5 + d8) + 1×(d3 + d6 + d9) must be a multiple of 10Reference
What each part of a routing number means
Every ABA routing number follows the same nine-digit layout.
| Positions | Section | What it identifies |
|---|---|---|
| 1–4 | Federal Reserve routing symbol | The Federal Reserve district and processing center that handles the item. |
| 5–8 | ABA institution identifier | The specific bank or credit union that holds the account. |
| 9 | Check digit | Calculated from the first eight digits using the mod-10 formula above. |
The first two digits show how the routing number is used:
| First 2 digits | Meaning |
|---|---|
| 00 | United States Government |
| 01–12 | Federal Reserve Bank — primary (one per district) |
| 21–32 | Thrift institutions (Federal Reserve district number + 20) |
| 61–72 | Electronic / ACH transactions (district number + 60) |
| 80 | Traveler's cheque |
The twelve Federal Reserve districts are: 01 Boston, 02 New York, 03 Philadelphia, 04 Cleveland, 05 Richmond, 06 Atlanta, 07 Chicago, 08 St. Louis, 09 Minneapolis, 10 Kansas City, 11 Dallas, 12 San Francisco.
Troubleshooting
Common routing number mistakes
If the checker reports an invalid number, it's usually one of these.
Transposed digits
Swapping two digits is the most common error. The checksum catches almost all of these.
Wrong routing for the method
Using the ACH routing number for a wire (or vice versa) when the bank publishes different numbers for each.
Using the account number
The routing number is the 9-digit number, usually the leftmost group printed along the bottom of a check.
Extra characters
Copying MICR symbols or spaces from a check or statement alongside the digits.
Good to know
Routing number vs account number vs SWIFT vs IBAN
A routing number only covers US payments. New to the rails themselves? See our guides to ACH payments and wire transfers.
Routing number
A 9-digit ABA code that identifies the US bank in ACH transfers, wires and checks. It is checksum-validated.
Account number
Identifies the individual account at that bank. Lengths and formats vary by bank and are not standardized by a single checksum.
SWIFT / BIC
An 8 or 11-character code used to route international transfers — a separate system from ABA. Check a SWIFT/BIC code with our free checker.
IBAN
Used across Europe and many other regions to identify an account for cross-border payments. Validate an IBAN with our free checker.