An ABA routing number (American Bankers Association routing transit number) is a 9-digit code that identifies a US bank or credit union in the domestic payment system. It is used for ACH transfers, check processing, and some domestic wire transfers. For international transfers, a SWIFT code (BIC) is typically required instead of — or in addition to — the ABA routing number.
Every ABA routing number is exactly 9 digits. The structure follows a specific format: digits 1-4 represent the Federal Reserve routing symbol (identifying the Fed district and processing center), digits 5-8 identify the specific bank (the ABA institution identifier), and digit 9 is a check digit calculated using a weighted modulus algorithm. Example: Bank of America's routing number 026009593 breaks down as: 0260 (Federal Reserve Bank of New York), 0959 (Bank of America institution code), 3 (check digit). Large banks may have multiple routing numbers for different regions — Chase alone has over 20 routing numbers, one per state or region where it operates.
The 9-digit format encodes specific information. Digit 1: Federal Reserve district (1-12, or 0 for government). Digits 2-4: Federal Reserve office and processing center. Digits 5-8: Specific bank identifier assigned by the ABA. Digit 9: Check digit, calculated as (3×d1 + 7×d2 + d3 + 3×d4 + 7×d5 + d6 + 3×d7 + 7×d8 + d9) mod 10 = 0. Common routing numbers you may recognize: Wells Fargo (121000248), Chase New York (021000021), Citibank (021000089), Bank of America California (121000358). If the first two digits are 00-12, it is a standard routing number. If the first two digits are 21-32, it designates a thrift institution (savings bank or credit union). Numbers starting with 61-72 are electronic transaction routing numbers.
There are five reliable ways to find your bank's routing number: 1. Bottom of a check: the first 9 digits printed in MICR (magnetic ink) at the bottom-left corner, before your account number. The routing number is enclosed between the ⑆ symbols. 2. Your bank's mobile app or online banking: look under "Account Details" or "Direct Deposit Setup." Most banks display the routing number prominently. 3. Google search: search for "[Your Bank Name] routing number." Banks publish their routing numbers on their websites. 4. Federal Reserve lookup: the Fed maintains the official routing number database at https://www.frbservices.org/EPaymentsDirectory/. Enter a bank name or routing number to verify. 5. Call your bank: customer service can confirm which routing number to use for your specific transaction type (ACH, wire, or check). Important: some banks use DIFFERENT routing numbers for ACH transfers vs wire transfers. Always confirm which type you need. Using the wrong one will delay or reject your transfer.
This is the most common source of confusion. In the US, there are essentially three types of routing numbers, and they sometimes differ for the same bank: ACH routing number: used for ACH transfers (direct deposit, bill pay, peer-to-peer). This is the most common type and what most people mean by "routing number." ACH transfers are free or cheap ($0-3) and take 1-3 business days. Wire routing number: used for domestic wire transfers via Fedwire. Some large banks have a separate wire routing number. Wire transfers cost $15-30 domestically and settle same-day. If your bank has a separate wire routing number and you use the ACH one for a wire, the transfer may be rejected. Check routing number: printed on physical checks in MICR format. This is almost always the same as the ACH routing number. For international transfers, none of these are relevant on the receiving end. You need the recipient bank's SWIFT/BIC code instead. However, if you are the sender in the US, your bank may need your ABA routing number to debit your account.
ABA routing numbers are exclusively for US domestic transfers. SWIFT codes (BIC — Bank Identifier Codes) are for international transfers. They serve the same purpose — identifying a bank — but in different systems. ABA routing number: 9 digits, numeric only, US banks only. Used for ACH, Fedwire, and check processing within the US. SWIFT/BIC code: 8 or 11 characters, alphanumeric, global. Used for international wire transfers via the SWIFT messaging network. Example: CHASUS33 (Chase New York). For sending money abroad from the US, the recipient's bank needs a SWIFT code (and IBAN in Europe, or local account number elsewhere). Your US bank may ask for your ABA routing number internally. Modern fintech providers like Wise handle all routing automatically — you just enter the recipient's bank details.
When receiving an international wire IN the US, give the sender: your bank's SWIFT code (e.g., BOFAUS3N for Bank of America), your ABA routing number (e.g., 026009593), and your account number. The sender's bank uses the SWIFT code to route the message internationally, and the US correspondent bank uses the ABA routing number for final domestic delivery. When sending money FROM the US internationally, you typically only need the recipient's bank details (SWIFT code + IBAN or local account number). Your bank handles the US side internally using your ABA and account number. This is why the confusion exists — both identifiers appear in the same transaction but serve different legs of the journey.
On the bottom-left of a check (first 9 digits), in your bank's app or website, or by searching your bank name + "routing number." Large banks may have different routing numbers for ACH vs wires.
No. ABA routing numbers identify US banks for domestic transfers. SWIFT codes (BIC) identify banks for international transfers. You need a SWIFT code to send money abroad, not an ABA routing number.
Yes — give the sender your ABA routing number AND account number so their bank knows which US bank to wire to. The sender's bank then uses a SWIFT code to find the route to your US bank.
Yes. The ABA routing number database is publicly available. You can look up routing numbers on the Federal Reserve's website or the ABA's routing number lookup tool.
Payments may be rejected or credited to the wrong account. Wire transfers are harder to reverse than ACH. Always verify routing numbers before sending.
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