ABA Routing Number Validator

How it is calculated

The tool strips everything that is not a digit, so spaces and dashes are fine, and then needs exactly nine digits. Number the digits d1 to d9 from the left and compute sum = 3×(d1 + d4 + d7) + 7×(d2 + d5 + d8) + 1×(d3 + d6 + d9). The number passes when the sum is divisible by 10.

This is only the checksum test for the format used by US ABA routing numbers. A pass means the digits are internally consistent, which catches most single-digit typos and many swapped neighbours. It does not tell you whether a bank actually uses that number, which institution it belongs to, or whether it supports ACH or wire transfers. Fewer or more than nine digits give no result. Routing formats in other countries (IBAN, sort codes, BSB) are different and will not validate here.

Common mistakes

• Treating Valid as proof that the account or bank exists. It only means the checksum works out; a made-up number can pass.
• Entering an account number or a card number instead of the nine-digit routing number. Those have different lengths and rules.
• Dropping a leading zero when copying from a spreadsheet. Routing numbers can start with 0, and a missing digit leaves eight digits, so there is no result.
• Using a number from outside the US. Sort codes, IBANs and SWIFT codes are not ABA routing numbers.
• Assuming a passing number is the right one for your payment. The checksum cannot tell which number to use for which kind of transfer, so confirm it with the bank.