MICR Routing Validator
Verify the checksum of a 9-digit ABA routing number and read the MICR code structure used on cheques.
How this tool works
A MICR routing number is the nine digit number on a US cheque that identifies the routing symbol, the ABA institution identifier and the check digit. The format is fixed: a four digit Federal Reserve routing symbol, a four digit ABA identifier for the institution, and one check digit computed with a 3-7-1 weighting.
The check digit is computed by multiplying the first eight digits alternately by 3 and 7, from the left, summing, and taking the remainder modulo 10. A valid routing number tells you the nine digits are well formed. It does not tell you the institution is still operating, and a number that was valid when issued can be retired.
Worked example
| Step | Value |
|---|---|
| Routing number | 021000021 |
| Federal Reserve routing symbol | 0210 |
| ABA institution identifier | 0002 |
| Check digit | 1 |
| Weighted sum | 3x0 + 7x2 + 1x1 + 3x0 + 7x0 + 1x0 + 3x0 + 7x2 = 21, remainder 1 |
A 21 remainder means the check digit is 1, because the total is brought up to the next multiple of 10.
When to use it
- Validate a routing number typed into a payment form
- Catch a transposition in a manually keyed routing number
- Confirm the format before a file is submitted to a bank
- Validate routing numbers in a batch import
Frequently asked questions
What is a MICR routing number?
The nine digit number on a US cheque that routes it to the paying institution. It contains a four digit Federal Reserve routing symbol, a four digit ABA institution identifier and a check digit.
How is the MICR check digit computed?
Multiply the first eight digits alternately by 3 and 7 from the left, sum them, and take the remainder modulo 10. The check digit brings the total up to the next multiple of 10.
Does a valid routing number mean the bank exists?
No. It means the digits are internally consistent. Routing symbols are retired and reassigned over time, so a number that was valid once may not be now.
Why do some routing numbers have a leading zero?
They are always nine characters. A shorter institution identifier is padded with a leading zero, which is why they are often lost when typed into a form.
Is a MICR routing number the same as a SWIFT BIC?
No. The routing number identifies a US institution for domestic clearing, while a SWIFT BIC identifies a bank internationally, and a bank has both, with different values.