Routing Number Reference
Validate an ABA routing number using the checksum algorithm.
How the checksum works
ABA routing numbers use a weighted checksum: (3*(d1+d4+d7)+7*(d2+d5+d8)+(d3+d6+d9)) mod 10 == 0.
How this tool works
A US routing number is a nine digit MICR code. The first four are the Federal Reserve routing symbol, which tells you which of the twelve Federal Reserve districts and which processing centre handle it, and the next four identify the institution within that district. The final digit is a check digit.
The two halves of the number answer different questions. The routing symbol tells you how the item is processed, and the ABA identifier tells you which institution it is for. Together they are enough to route a payment domestically, and the check digit catches the transcription errors that nine digits typed by hand inevitably produce.
How the number is structured
| Digits | Meaning |
|---|---|
| 0 to 3 | Processing centre in the first Federal Reserve district |
| 4 to 8 | Processing centre in the second district |
| 9 to 12 | Processing centre in the third district |
| 21 to 32 | Thrift institutions, processed by the thrift processing centre |
| 61 to 72 | Electronic transactions |
| 80 to 98 | Traveler's cheque and money order drafts |
The first two digits are the ABA's classification of the institution, and the check digit is always a single digit at the end.
When to use it
- Route a domestic payment to the right institution
- Check a routing number typed into a form
- Identify the processing centre for a number
- Reconcile a payments file against a bank's list of codes
Frequently asked questions
How many digits is a routing number?
Always nine, with a leading zero where the institution identifier is shorter.
What do the first four digits mean?
The Federal Reserve routing symbol, which identifies the processing centre and the Federal Reserve district that handles the item.
How do I check a routing number?
Multiply the first eight digits alternately by 3 and 7 from the left, sum them, and check that the last digit brings the total to a multiple of 10.
Can two banks have the same routing number?
No, but a routing symbol can be retired and its codes reassigned to a different institution, so a number that was valid once may point somewhere else now.
What is a MICR line?
The line of magnetic ink characters at the bottom of a cheque, which carries the routing number, the account number and the cheque number in a machine-readable form.