A routing number has nine digits
Every routing number in the United States contains exactly nine digits. Banks, credit unions, and other financial institutions each have one routing number that identifies them to the Federal Reserve and the clearing system that moves money between accounts.
The nine digits are not random. They follow a specific structure set by the American Bankers Association, and each position tells the clearing system something different about where the money is going. The first four digits identify the Federal Reserve district and the bank's location within it. The next four digits are the bank's own identifier. The last digit is a check digit—a mathematical verification that the first eight digits were entered correctly.
You will see routing numbers written with or without hyphens (for example, 021000021 or 021-000-021), but the hyphens are just formatting. The actual number is always nine digits with no letters.
Key Takeaways
- A routing number is always nine digits long, with no exceptions across U.S. banks and credit unions.
- The first four digits identify the Federal Reserve district and the bank's region; the next four identify the specific bank; the last digit verifies the number is correct.
- Routing numbers may be written with hyphens for readability, but the hyphens are not part of the actual number.
- You can find your routing number on the bottom left of a check, through your bank's website, or by calling your bank directly.
Where the nine digits come from
The American Bankers Association created the routing number system in 1910, long before computers made instant transfers possible. The nine-digit format was designed to work with the mechanical sorting machines banks used at the time, and the format has stayed the same ever since.
The first two digits represent the Federal Reserve district—there are 12 districts across the country, so these digits range from 01 to 12. The third and fourth digits narrow it down further to the specific region or state within that district. Digits five through eight identify the individual bank or credit union. The ninth digit is calculated from the first eight using a mathematical formula, so if you enter a routing number with a typo in the first eight digits, the ninth digit will not match and the system will catch the error.
This structure means that if you know a bank's routing number, you can tell which Federal Reserve district it belongs to and roughly where it operates. However, the system is not perfectly geographic anymore—banks have merged, moved, and expanded across state lines, so the routing number does not always reflect where a bank is headquartered today.
How to find your nine-digit routing number
The easiest place to find your routing number is on a check from your checking account. Look at the bottom left corner of the check. You will see three groups of numbers separated by special symbols. The first group of nine digits is your routing number. The second group is your account number. The third group is the check number.
If you do not have a check handy, log into your bank's website or mobile app. Most banks display the routing number in the account details section, often labeled "Routing Number," "ABA Number," or "Transit Number." You can also call your bank's customer service line and ask for your routing number—they will give it to you over the phone.
Some banks have more than one routing number if they operate in multiple states or have acquired other banks. Make sure you are using the routing number for the specific branch or account type you need. Your bank's website will usually let you filter by branch or account type to find the correct nine-digit number.
Why the nine-digit format matters for transfers
When you set up a direct deposit, wire transfer, or automatic payment, you will need to provide both your routing number and your account number. The routing number tells the sending bank which institution to send the money to. Your account number tells that institution which specific account within the bank should receive the funds.
If you enter a routing number with the wrong number of digits—say, eight or ten instead of nine—the transfer will be rejected before it even leaves your bank. The check digit at the end catches most typos automatically. This built-in error detection has prevented countless misdirected payments over the decades.
The nine-digit standard also makes routing numbers compatible with the ACH (Automated Clearing House) system, which processes most electronic transfers in the U.S., and with wire transfer systems used by the Federal Reserve. Every financial institution that participates in these systems uses the same nine-digit format, which is why the standard has remained unchanged since 1910.
Routing numbers versus account numbers
It is easy to confuse a routing number with an account number because they both appear on your check and both are needed for transfers. The routing number is nine digits and identifies your bank. Your account number is usually 10 to 12 digits (though this varies by bank) and identifies your specific account within that bank.
Think of it this way: the routing number is like the address of the bank building. The account number is like your apartment number inside that building. Together, they tell the clearing system exactly where to send your money.
When you are setting up a transfer, the form will usually have separate fields for routing number and account number. If you put the account number in the routing number field, the transfer will fail because the system will not recognize the number as a valid nine-digit routing code.
What happens if you use the wrong routing number
If you enter an incorrect routing number on a transfer, one of two things will happen. If the nine digits do not pass the check-digit verification, your bank will reject the transfer before it leaves. If the nine digits are valid but belong to a different bank, the transfer may go through to that bank, but it will not match any account there and will eventually be returned to you.
Returned transfers usually take three to five business days to come back to your account. During that time, the money is in limbo, and you may not see it in your balance. Some banks charge a fee for a returned transfer, though many waive the fee if it was the bank's error.
The safest approach is to double-check the routing number before you submit any transfer. Verify it against your check, your bank's website, or a call to customer service. The nine-digit format makes it easy to spot obvious errors—if someone gives you a routing number with eight or ten digits, you know immediately it is wrong.
Frequently Asked Questions
Can a routing number have letters in it?
No. A routing number is always nine digits only, with no letters. If you see letters mixed in with numbers, it is not a routing number. You may be looking at an account number, a reference code, or something else entirely.
Do all banks in the same state share the same routing number?
No. Each bank or credit union has its own routing number, regardless of state. Some large banks have multiple routing numbers if they operate in different regions or have acquired other institutions. Always use the routing number for your specific bank and branch.
Is the routing number the same as the ABA number?
Yes. ABA stands for American Bankers Association, the organization that created the routing number system. "Routing number" and "ABA number" refer to the same nine-digit code. You may see either term used on bank websites or forms.
What does the last digit of a routing number do?
The last digit is a check digit calculated from the first eight digits using a mathematical formula. It allows the system to verify that the routing number was entered correctly. If the first eight digits are wrong, the ninth digit will not match, and the transfer will be rejected.
Can I find someone else's routing number if I know their bank?
Yes. Routing numbers are public information. You can search for any bank's routing number on the Federal Reserve's website, on your bank's website, or through a simple online search. You need the routing number to send money to someone, so it is not secret the way a password is.