Validate routing numbers and US bank account formats instantly. Free ABA routing checker with checksum and bank lookup.
Learn how this works →Bank Details
Paste full bank details — routing number (ABA) and account will be detected automatically.
This tool validates format only. It does not verify whether the bank account exists or can receive payments.
scroll for examples & details ↓
Enter the 9-digit ABA routing number — found at the bottom left of any US check.
Enter the bank account number (4–17 digits) — found to the right of the routing number on the check.
Green means structurally valid. Red means a format or checksum error was detected.
Format check only
This tool checks format only. It validates routing number structure and ABA checksum, but does not confirm that a bank account exists, is active, belongs to a person, or can receive payments. It does not perform financial, identity, or bank verification.
How this routing number check works
An ABA routing transit number (RTN) is a 9-digit code used to identify a US financial institution in a bank transfer. Created by the American Bankers Association in 1910, routing numbers tell the Federal Reserve which bank should receive funds in an ACH payment or wire transfer. Every US bank has at least one routing number; large banks often have several — one per region or transaction type. The routing number appears at the bottom left of every US paper check, as the first number in the MICR line.
Always exactly 9 digits — no more, no less
First 2 digits encode the Federal Reserve district (01–12, 21–32, 61–72, 80)
Digits 3–8 identify the specific financial institution
Digit 9 is a check digit computed using the ABA 3-7-1 weighted sum formula
Found at the bottom-left corner of every US paper check
Large banks may have different routing numbers for ACH vs wire transfers
ABA routing number validation uses a three-step process. First, the number must be exactly 9 digits. Second, the first two digits must fall within valid Federal Reserve district codes. Third, the 9 digits must satisfy the ABA weighted checksum: multiply the first digit by 3, the second by 7, the third by 1, repeating this 3-7-1 pattern across all 9 digits, then sum the results. The total must be divisible by 10. This checksum catches most transcription errors — a single wrong digit will almost always produce a different total.
Length check
The routing number must be exactly 9 digits. Any input shorter or longer fails immediately.
Prefix check
The first two digits encode the Federal Reserve district. Valid prefixes are 01–12, 21–32, 61–72, and 80. Any other prefix is structurally invalid.
ABA checksum
The 9 digits pass through the 3-7-1 weighted formula: (3×d₁ + 7×d₂ + d₃ + 3×d₄ + 7×d₅ + d₆ + 3×d₇ + 7×d₈ + d₉) mod 10 = 0. A valid routing number always satisfies this equation.
US bank-to-bank transfers move money through two main systems. ACH (Automated Clearing House) is the network used for payroll direct deposits, bill payments, and peer-to-peer transfers — it typically settles in 1–3 business days and is low cost. Wire transfers are processed individually and settle the same business day; they are used for larger or time-sensitive payments and carry higher fees. Both systems require a valid ABA routing number and account number to route the funds. International transfers to or from other countries typically use SWIFT BIC codes and IBAN numbers instead.
These are real routing numbers for major US banks. They are public information, printed on checks and published on bank websites.
021000021
JPMorgan Chase
NY
026009593
Bank of America
NY
121000248
Wells Fargo
CA
031000053
PNC Bank
PA
051000017
Capital One
VA
The routing number identifies the financial institution (which bank); the account number identifies the specific account within that bank. You need both to make a US bank transfer. The routing number is semi-public — all customers of the same bank branch typically share it, and it is printed openly on checks. The account number is private — it uniquely identifies your account and should be protected. Together they form the complete address of a bank account in the US payment system. If someone only gives you a routing number, you do not have enough information to initiate a transfer.
Even a single wrong digit causes a checksum failure. These are the most frequent causes:
An ABA routing number is used for domestic US transfers within the ACH and wire systems. An IBAN (International Bank Account Number) is used in Europe and many other countries for international transfers. The US does not participate in the IBAN system — if you are making a transfer to or from the US, you will need a routing number and account number, not an IBAN. If you are sending money internationally from the US, you will typically need the recipient's SWIFT BIC and account number instead.
An ABA routing number is a 9-digit code assigned by the American Bankers Association to identify US financial institutions. It is used in ACH transfers, wire transfers, and check processing to route funds to the correct bank.
The routing number is the first 9-digit number at the bottom left of any US paper check, in the MICR line. It is also available in your online banking portal, on your bank's website, or by calling customer service.
Large US banks often maintain separate routing numbers for different states (inherited from bank mergers) or different transaction types — ACH, domestic wire, and international wire may each use a different routing number. Always confirm with your bank which routing number applies to your specific transfer type.
ACH (Automated Clearing House) transfers are processed in batches and typically settle in 1–3 business days. They are used for payroll direct deposits, bill payments, and peer-to-peer transfers. Wire transfers are processed individually, settle the same business day, and are used for larger or time-sensitive payments. Both use ABA routing numbers.
These pages go deeper into individual topics without duplicating the validator itself.
Check routing number with the ABA validator →What Is an ABA Routing Number?
Everything you need to know about ABA routing transit numbers — their structure, history, how they are assigned, and how they differ from account numbers.
How to Read a US Check — Finding Routing and Account Numbers
A step-by-step guide to the MICR line on the bottom of a US check, including where to find the routing number, account number, and check number.
ACH vs Wire Transfer — What's the Difference?
A practical comparison of ACH and wire transfers — how each works, when to use which, typical costs, settlement times, and routing number requirements.
Routing Number vs Account Number — What's the Difference?
A clear explanation of what routing numbers and account numbers do, how they work together, and how to keep your account number secure.
Common Routing Number Errors and How to Fix Them
The most frequent mistakes people make with ABA routing numbers — wrong length, transposed digits, wrong routing number type, and how each error affects your transfer.
IBAN vs ABA Routing Number — International vs US Bank Transfers
A complete comparison of IBANs and ABA routing numbers — what each identifies, where each is used, and how to determine which one you need for a payment.