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Routing Number Validator

Finance & Global IDs

Validate US ABA routing numbers using the official checksum algorithm instantly. Decodes the Federal Reserve district and institution type — client-side only.

Reviewed by the thecalcu.com team · Last updated July 16, 2026

What is a Routing No.?

The Routing Number Validator checks whether a US ABA routing number satisfies the official 3-7-1 weighted checksum algorithm and uses a valid Federal Reserve district prefix. A routing number is the 9-digit identifier that tells the US financial system which bank holds an account, used in ACH direct deposits, wire transfers, automatic bill payments, and cheque processing.

The validator performs two checks:

  1. Federal Reserve district prefix, the first two digits must be one of the 24 valid district codes (01–12 for standard institutions, 21–32 for electronic-only participants)
  2. ABA 3-7-1 checksum, the weighted sum 3(d1+d4+d7) + 7(d2+d5+d8) + 1(d3+d6+d9) must be divisible by 10

These checks catch the most common errors: digit transpositions (which almost always break the checksum), wrong digit count, and account number accidentally entered instead of routing number.

What it does not check: Whether the specific routing number is currently assigned to an active financial institution. The checksum confirms the number was issued correctly by the ABA; active assignment requires querying the Federal Reserve's E-Payments Routing Directory. Use the IBAN Validator for European bank accounts and the IFSC Code Validator for Indian NEFT/RTGS routing.

All validation is client-side. No data is transmitted.

Why Use a Routing Number Validator?

Routing number errors in direct deposit and wire transfer instructions cause failed or misdirected payments. A transposed digit is the most common error, it feels correct to the eye but fails the checksum immediately.

Payroll use case: An Indian company setting up US payroll for remote employees needs to collect routing numbers for ACH direct deposit. A validator at the form input level catches transpositions and account-number-instead-of-routing-number errors before they reach the payroll processor, preventing rejected ACH transactions and the fees associated with returned items.

Banking integration use case: A fintech developer building a US bank account verification flow uses the routing number checksum as a first-pass filter before making an expensive third-party micro-deposit verification call, rejecting obviously invalid numbers instantly without any API cost.

Who Should Use This Validator?

Developers building US payroll, ACH payment, or direct deposit features who need a fast client-side routing number filter before passing values to a payment processor or bank API.

Finance and HR teams at Indian companies processing US employee or contractor payments via ACH who want to validate routing number format before submitting payroll runs.

Accountants and bookkeepers verifying bank details on US vendor payment instructions before initiating wire transfers.

Fintech product teams building US consumer banking products where users enter routing numbers for external account linking.

What Insights Does the Routing Number Validator Give You?

A valid result shows the Federal Reserve Bank district identified by the first two digits, for example, prefix 02 identifies the Federal Reserve Bank of New York, and prefix 12 identifies the Federal Reserve Bank of San Francisco. This geographic attribution is a useful sanity check: a bank account for a California business should ideally have a routing number from Federal Reserve District 12 (San Francisco), not District 01 (Boston).

An invalid result specifies the failure: wrong digit count, invalid Federal Reserve prefix, or failed checksum. A failed checksum usually means a transposed digit; the error message includes the checksum formula to help developers understand the algorithm.

How to use this Routing No. calculator

  1. Enter the routing number in the input field, exactly 9 digits (e.g. 021000021).
  2. Check the Valid/Invalid badge, updates instantly.
  3. Read the details, Federal Reserve district and checksum result.
  4. If invalid: check for transposed digits and verify against the bank's official routing number page.
  5. If you need active institution verification: query the Federal Reserve's E-Payments Routing Directory.
Show formula & methodology ↓Show less ↑

Formula & Methodology

ABA 3-7-1 checksum:

checksum = 3×(d1+d4+d7) + 7×(d2+d5+d8) + 1×(d3+d6+d9) valid if: checksum % 10 === 0

Where d1 through d9 are the individual digits left to right.

Example: 021000021
d = [0, 2, 1, 0, 0, 0, 0, 2, 1] 3×(0+0+0) + 7×(2+0+2) + 1×(1+0+1) = 3×0 + 7×4 + 1×2 = 0 + 28 + 2 = 30 30 % 10 = 0 ✓ Valid

Federal Reserve district codes:

| Prefix | Federal Reserve Bank |
|---|---|
| 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 |
| 21–32 | Electronic-only equivalents |

Valid and invalid examples:

| Routing Number | Valid? | Note |
|---|---|---|
| 021000021 | ✓ | JPMorgan Chase NY, checksum passes |
| 021000012 | ✗ | Transposed last two digits, checksum fails |
| 12345678 | ✗ | Only 8 digits |
| 099999999 | ✗ | Prefix 09 not a valid Federal Reserve district |

Related Tools

You may also find these useful: SWIFT / BIC Code Validator.

Frequently Asked Questions

What is an ABA routing number?
An ABA routing number (also called an ABA routing transit number or RTN) is a 9-digit code that identifies a US financial institution for the purpose of processing financial transactions. It was created by the American Bankers Association (ABA) in 1910. Routing numbers are used for wire transfers, ACH direct deposits, automatic bill payments, and paper cheque processing. Every US bank and credit union has at least one routing number.
What is the format of a routing number?
A routing number is exactly 9 digits with no separators. The first two digits identify the Federal Reserve district (01–12 for standard, 21–32 for electronic-only institutions). The next six digits are the bank's ABA institution identifier. The 9th digit is a check digit calculated from the preceding 8 digits using a weighted checksum. Example: 021000021 is JPMorgan Chase Bank's New York routing number.
How does the ABA routing number checksum work?
The checksum uses a 3-7-1 weighting: multiply the 1st, 4th, and 7th digits by 3; multiply the 2nd, 5th, and 8th digits by 7; multiply the 3rd, 6th, and 9th digits by 1; sum all nine products. A valid routing number produces a sum divisible by 10. This is a simple but effective error-detection mechanism, a single digit transposition almost always produces a checksum failure.
Can a bank have multiple routing numbers?
Large banks often have multiple routing numbers for different purposes or different geographic regions. For example, Bank of America has different routing numbers for California (121000358), Texas (111000025), and other states. Some banks have separate routing numbers for wire transfers versus ACH direct deposits. Always use the routing number that corresponds to the transaction type and the account's home state.
Does this validator confirm the routing number is active?
No, the validator runs the ABA checksum algorithm and checks the Federal Reserve district prefix. A passing checksum confirms the number is structurally correct and was legitimately issued by the ABA. It does not confirm the number is currently assigned to an active institution or that the institution is still operating. The Federal Reserve's E-Payments Routing Directory (a free public database) can be used for active status verification.
What is the difference between a routing number for ACH and for wire transfers?
Some banks use different routing numbers for ACH transactions (direct deposit, bill pay) and domestic wire transfers. The routing number printed on a paper cheque is typically the ACH routing number. For a domestic wire transfer, banks sometimes require a different routing number, check your bank's website or call them to confirm which routing number to use for wire transfers specifically.
Is my routing number data stored when I validate it?
No, all validation runs entirely in your browser. The routing number is never sent to any server, stored, or logged. The tool works offline once loaded.
What is the routing number format outside the US?
Routing numbers are US-specific. The equivalent for European bank accounts is the IBAN (International Bank Account Number) combined with a SWIFT/BIC code. India uses IFSC codes for NEFT, RTGS, and IMPS transactions. UK accounts use Sort Codes (6 digits). Australian accounts use BSB codes (6 digits). Use the [IBAN Validator](/iban-validator/) for European accounts and the [IFSC Code Validator](/in/ifsc-validator/) for Indian accounts.
How do I use the Routing Number Validator?
Enter the 9-digit routing number in the input field (no hyphens needed). The validator runs the 3-7-1 checksum immediately and checks the Federal Reserve district prefix. The Valid/Invalid badge updates instantly. The details panel shows the Federal Reserve Bank district identified by the prefix, and confirms whether the checksum passed.
Where do I find my bank's routing number?
Your routing number appears on the bottom-left of your paper cheques, in your bank's mobile app (usually under account details), on your bank's website, and on your bank statement. The 9 digits at the bottom of a cheque from left to right are: routing number, account number, cheque number, the routing number is the first set, enclosed in transit symbols (⑆ before and after in MICR font).
Why do some routing numbers fail the checksum even though they look valid?
The most common reason is a digit transposition, two adjacent digits swapped (e.g. 021000012 instead of 021000021). Transpositions almost always change the checksum. Another common cause is confusing the routing number with the account number, which appears immediately to the right of the routing number on a cheque. If a routing number fails the checksum, verify it digit by digit against the cheque or your bank's official documentation.
Also known as
check routing numberABA routing number validatorbank routing number checkerACH routing numberdirect deposit routing number