BYTETOOLS

ABA Routing Number Validator

Validate a 9-digit US bank routing number with the ABA checksum, calculate a missing ninth digit, and decode what the first two digits mean.

This is a structural check. It confirms the ABA checksum and reads the meaning of the first two digits — it cannot tell you which bank a number belongs to or whether it is still in service, because no bank directory is consulted. Everything runs locally in your browser.

Result

Enter a routing number above and the checksum, the Federal Reserve range and the cheque fields appear here.

What is the ABA Routing Number Validator?

The ByteTools ABA Routing Number Validator applies the checksum every US routing transit number must satisfy: three times the first, fourth and seventh digits, plus seven times the second, fifth and eighth, plus the third, sixth and ninth, all adding up to a multiple of ten.

  • Full ABA 3-7-1 checksum with the arithmetic written out
  • Calculates the missing ninth digit from an eight-digit prefix
  • Decodes the prefix into its Federal Reserve district or range
  • Splits the number into routing symbol, institution identifier and check digit
  • Batch validation with a copyable, tab-separated report
  • Structural checking only — no bank lookup, nothing uploaded

How to use the ABA Routing Number Validator

  1. 1

    Type or paste the nine-digit routing number — it is the bottom-left number on a US cheque.

  2. 2

    Read the verdict and, if it fails, the digit the checksum says should be at the end.

  3. 3

    Enter only the first eight digits to have the ninth calculated for you.

  4. 4

    Check the prefix panel to see which Federal Reserve range the number falls in.

  5. 5

    Paste a list into the batch box for one verdict per line.

About the ABA Routing Number Validator

The ByteTools ABA Routing Number Validator applies the checksum every US routing transit number must satisfy: three times the first, fourth and seventh digits, plus seven times the second, fifth and eighth, plus the third, sixth and ninth, all adding up to a multiple of ten. Enter only eight digits and the tool works out the ninth for you.

It also reads the first two digits, which are not arbitrary. Values from 01 to 12 map to the twelve Federal Reserve districts, 21 to 32 mark thrift institutions in those same districts, 61 to 72 are electronic-only identifiers used for ACH and wires, and 80 is reserved for traveller's cheque issuers. Everything else is unassigned, which is a useful early warning that a number is fabricated.

This is a structural check only — no bank directory is consulted, so it cannot tell you which institution a number belongs to or whether it is still in service. Everything runs 100% locally in your browser, so account details you paste are never uploaded or logged.

Frequently asked questions

How do you validate a routing number?

Multiply the first, fourth and seventh digits by 3, the second, fifth and eighth by 7, and add the third, sixth and ninth as they are. If the total divides evenly by ten, the number passes the ABA checksum.

Can this tell me which bank a routing number belongs to?

No. Matching a number to an institution needs the Federal Reserve's E-Payments directory, which this offline page never contacts. It can only tell you the number is well formed and which Federal Reserve range the prefix falls in.

What do the first two digits of a routing number mean?

They identify the issuing Federal Reserve district and the type of institution. Values from 01 to 12 are the primary districts, 21 to 32 mark thrift institutions in those same districts, and 61 to 72 are electronic-only identifiers used for ACH and wires. The value 80 is reserved for traveller's cheque issuers, and everything else is unassigned.

Why do banks have more than one routing number?

Large banks often hold separate numbers for different states, for paper cheques versus ACH, and for domestic wires. Merged banks also keep the acquired institution's numbers alive for years, so several valid numbers can all reach the same bank.

Is it safe to enter my routing number here?

Yes. The check runs in your browser with JavaScript and nothing is transmitted, logged or stored. A routing number is public information anyway — it is printed on every cheque a bank issues.

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