Routing Number Checker

Instantly check whether a 9-digit US bank routing number (ABA number) passes the official checksum formula used on checks, direct deposits, and ACH transfers — with every step of the math shown. Runs entirely in your browser, nothing is ever sent to a server.

🔒 Privacy: The routing number you enter is checked only with JavaScript running in your browser. It is never sent to a server, logged, or written into the page's URL. This is not a bank lookup or account-verification service — it is a mathematical format/checksum check only.

Routing number

Only digits — spaces and dashes are ignored automatically. Usually found at the bottom-left of a check.

9Digits in a US routing number

3-7-1Checksum weighting pattern

mod 10 = 0Result required for a valid checksum

12Original Federal Reserve districts

⚠️ Important — scope note: This tool performs a mathematical format/checksum check only. A "valid" result confirms the 9 digits are structurally well-formed according to the public ABA checksum algorithm — it does not confirm that the number belongs to a real, currently operating bank, or that any account exists. It is not a bank-verification, KYC, or account-lookup service, and it includes no live bank database or lookup capability. To confirm a specific bank's routing number, use an official bank statement, a voided check, or the bank's own website.

🏦 Routing Number Checker — ToolPico ↗

What is a routing number, and how is it checked?

A full explanation of the ABA routing number, the checksum formula behind the 9th digit, and where to find your own on a check.

A routing number — formally an ABA routing transit number — is a 9-digit code introduced by the American Bankers Association in 1910 so that checks and payments could be automatically routed to the correct bank. Today it's used for direct deposit, ACH transfers (like bill pay and payroll), and — sometimes with a different number for the same bank — wire transfers. This tool checks the format and checksum instantly, entirely in your browser.

What are the 9 digits made of?

Quick answerThe first 4 digits are the Federal Reserve routing symbol (historically tied to a Fed district and processing office), the next 4 digits identify the specific bank (the ABA institution identifier), and the 9th digit is a check digit mathematically derived from the first eight — that's the digit this tool's checksum verifies.

The ABA checksum formula, step by step

Quick answerLabel the digits d1 through d9 left to right. Multiply d1, d4, d7 by 3; multiply d2, d5, d8 by 7; multiply d3, d6, d9 by 1. Add all nine weighted values together. If the total is evenly divisible by 10 (remainder 0), the routing number passes the checksum.

Group 1 (weight ×3): positions 1, 4, and 7.
Group 2 (weight ×7): positions 2, 5, and 8.
Group 3 (weight ×1): positions 3, 6, and 9 — this includes the check digit itself.
Pass condition: (3×group1 + 7×group2 + 1×group3) mod 10 = 0.

Example: for 021000021, the weighted sum works out to 30, and 30 mod 10 = 0 — so it passes. Change any single digit and the check almost always fails, which is exactly what the check digit is designed to catch.

Where do I find my routing number on a check?

Quick answerIt's the first group of numbers in the MICR line — the machine-readable line of characters along the bottom-left of a check. The 9-digit routing number comes first, followed by your account number, then the check number.

⑆021000021⑆Routing number

⑈0123456789⑈Account number

1001Check number

You can also find your routing number in your bank's mobile app, on a monthly statement, or by calling the bank directly — useful if you don't have a paper check handy.

Routing number reference tables

The checksum weighting pattern, the historical Federal Reserve district prefix ranges, and a short illustrative list of major banks' publicly known routing numbers.

ABA checksum weight per digit position
Position	Digit	Weight
1st	`d1`	× 3
2nd	`d2`	× 7
3rd	`d3`	× 1
4th	`d4`	× 3
5th	`d5`	× 7
6th	`d6`	× 1
7th	`d7`	× 3
8th	`d8`	× 7
9th (check digit)	`d9`	× 1

Source: publicly documented ABA routing-number checksum specification. The nine weighted values are summed, and the total must be evenly divisible by 10.

Historical Federal Reserve district prefixes (informational, not a hard validity rule)
Prefix range	Meaning
`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`	Thrift/savings institutions (same district order, second series)
`61–72`	Electronic-only duplicate series (introduced for ACH processing)
`80`	Traveler's check issuers

This table is historical/reference context only. This tool treats the checksum as the authoritative validity check; the prefix range is shown as an informational note and never overrides the checksum result.

Illustrative examples — publicly published routing numbers of a few major US banks
Bank	Routing number
Bank of America	`026009593`
JPMorgan Chase	`021000021`
Wells Fargo	`121000248`
Citibank	`021000089`
U.S. Bank	`091000022`
PNC Bank	`043000096`
Capital One	`051405515`
TD Bank	`011400071`

Reference only, not exhaustive — large banks often have multiple routing numbers by state or by transfer type (ACH vs. wire). Always confirm the correct one on your own statement or check before using it for a real transfer.

Routing number terms glossary

Short definitions of the core concepts around US bank routing numbers.

ABA routing numberA 9-digit code assigned to identify the specific US bank or credit union responsible for a payment.

Routing transit number (RTN)Another common name for the same 9-digit routing number, used interchangeably across banks and payment systems.

MICR lineThe magnetic-ink, machine-readable line at the bottom of a check containing the routing number, account number, and check number.

ACH (Automated Clearing House)The US electronic network for direct deposits and bill pay, which relies on routing numbers to move funds between banks.

Wire transfer routing numberSome banks use a separate routing number for same-day wires than the one printed on checks — always confirm which is needed.

Federal Reserve routing symbolThe first four digits of a routing number, historically tied to a Federal Reserve district and processing office.

Check digitThe 9th and final digit, mathematically derived from the first eight so common writing/typing errors can be caught automatically.

Direct depositA payment, like a paycheck, sent electronically to a bank account — requires both a routing number and an account number.

SWIFT / BIC codeA different, 8–11 character code used for international wire transfers; not the same format or purpose as a domestic routing number.

Account numberThe number identifying an individual account at the bank named by the routing number; this tool does not check account numbers.

In-depth guides

Detailed answers to the most common routing-number questions.

How to find your routing number without a check

If you don't have a paper check handy, your routing number is almost always visible in your bank's mobile app (usually under account details) and on a monthly statement. You can also call your bank's customer service line and ask directly, or check the bank's official website, which typically lists routing numbers by state.

Be careful with search-engine results claiming to "look up" a routing number for a bank — always cross-check what you find against an official source like your own statement before using it for a real transfer.

Routing number vs. account number vs. SWIFT/BIC — what's the difference?

A routing number (9 digits) identifies the bank itself. An account number (typically 8–17 digits, varies by bank) identifies your specific account at that bank. Together, the pair is what's needed for a domestic direct deposit or ACH transfer.

A SWIFT/BIC code is a completely different, alphanumeric identifier (8 or 11 characters) used for international wire transfers instead of a routing number. Domestic US routing numbers and SWIFT/BIC codes are not interchangeable and use entirely different check-digit schemes.

What happens if I use the wrong routing number?

Most of the time, an incorrectly formatted routing number (one that fails the checksum) is simply rejected by the receiving bank or the ACH network before any money moves, and the payment bounces back or fails outright. That's exactly the purpose of the check digit — catching typos before they cause a problem.

In rarer cases, a routing number that happens to pass the checksum but belongs to a different bank than intended could send a payment toward the wrong institution, which is why this tool's checksum result is explicitly not a substitute for double-checking the number against your actual bank statement or a voided check.

Frequently asked questions

What is a routing number?

A routing number (also called an ABA number or routing transit number) is a 9-digit code that identifies the specific bank or credit union involved in a US financial transaction. It's used on checks, for direct deposit, ACH transfers, and — sometimes with a different number for the same bank — wire transfers.

How many digits does a US routing number have?

Exactly 9 digits, always. If a number you have is shorter or longer than 9 digits, it isn't a validly formatted US routing number, regardless of what the checksum says.

How do I check if a routing number is valid?

Enter the 9 digits into the checker above. It runs the public ABA checksum formula — 3×(d1+d4+d7) + 7×(d2+d5+d8) + 1×(d3+d6+d9) — and the number is considered validly formatted if that total is evenly divisible by 10 (remainder 0). The tool shows every step of the math so you can verify it by hand too.

Does a valid checksum mean the bank is real?

No. A passing checksum only means the 9 digits are mathematically self-consistent with how real routing numbers are constructed — it is a format check, not a bank lookup. It does not confirm the number is currently assigned to an active, operating bank. To confirm ownership, check a real bank statement, a voided check, or the bank's official website.

Where do I find my routing number on a check?

It's the first group of numbers printed along the bottom-left of a check, in the MICR line. The 9-digit routing number comes first, followed by your account number, and then the check number.

Do banks have more than one routing number?

Often, yes. Many banks use different routing numbers by state or region, and some use a separate routing number for wire transfers than the one printed on checks, which is typically used for ACH and direct deposit. Always check which type of transfer you're making before using a routing number.

What's the difference between a routing number and a SWIFT/BIC code?

A routing number is a 9-digit, US-only code used for domestic transfers such as ACH, checks, and direct deposit. A SWIFT/BIC code is an 8–11 character alphanumeric code used to identify banks for international wire transfers. The two are not interchangeable, and this tool's checksum only applies to the 9-digit ABA format.

Is it safe to share my routing number?

Yes — a routing number only identifies your bank, not your specific account, and it's printed on every check you write and routinely given to employers and billers for direct deposit. It's your account number, combined with the routing number, that should be treated more carefully, similar to any other financial account identifier.

Does this tool store or send my routing number anywhere?

No. All checking happens locally in your browser with JavaScript running on your device. Nothing you type is transmitted to a server, logged, or written into the page's URL. This tool is not a bank verification, KYC, or account-lookup service — it performs a math and format check only.

How does the bank-name match work, and is it a real bank lookup?

When a routing number you enter matches an entry in a small embedded reference table of roughly 180 well-known US banks and credit unions, the result shows which bank that number is publicly associated with. This table is illustrative and non-exhaustive — most valid routing numbers will not have a match — and it is not a live or official bank-lookup, KYC, or account-verification service. Always confirm a routing number against your own bank statement, a voided check, or the bank's official website before using it.

Can I generate a fake routing number for testing?

Yes. The checker includes an optional test/dummy routing number generator that produces a random 9-digit number engineered to pass the ABA checksum, intended purely for QA and development use — for example, populating a test form without using a real customer's data. The generated number is not a real bank routing number, is not guaranteed to be unassigned, and should never be used for an actual transfer.

Methodology & sources

ToolPico's Routing Number Checker is a free, independent tool. It implements the publicly documented ABA (American Bankers Association) checksum algorithm assigned to US bank routing numbers — verifying the 9-digit format and the check-digit math entirely in your browser, with no external library and no server round-trip.

Sources: American Bankers Association routing-number specification · Federal Reserve routing-number district reference. Last updated: July 21, 2026. This tool checks format/checksum validity only; it does not query any bank database or the official routing-number registrar, and the Federal Reserve district prefix table is provided as historical/informational context, not as a pass/fail rule.

What is a routing number, and how is it checked?

What are the 9 digits made of?

The ABA checksum formula, step by step

Where do I find my routing number on a check?

Routing number reference tables

Routing number terms glossary

In-depth guides

Frequently asked questions

Methodology & sources

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