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Credit Card Validator · Card Number and Routing Number Checker

A card number is not random. Its first digits name the card network, its length depends on the network and its last digit is a check digit calculated from all the others with the Luhn algorithm. That is how a website can tell you instantly that you mistyped a digit, before it asks a bank anything. This tool runs the same checks: it finds the network, checks the length for that network, runs the Luhn checksum and, if the number fails, tells you which digit would make it pass.
The second mode checks a US bank routing number, the 9-digit number at the bottom left of a check. It uses the 3-7-1 weighted checksum that the American Bankers Association defined, and it reads the first two digits as a Federal Reserve routing symbol to show the type of institution and the Federal Reserve district. A routing number is a public identifier of a bank, not a secret. Account numbers have no standard checksum, so they cannot be validated this way.
These are format checks only. A number that passes is well formed, but it can still belong to no card, a closed account or a stolen card, and the tool cannot tell. It also cannot say whether a card is debit, credit or prepaid, because that is not in the number and needs the issuer's own data. The check runs in your browser and the number is not stored, but you do not need to type a real card here: use a test number from the buttons.
Digits only, or with spaces and dashes. Checked in your browser and not stored. Try a test number below
Test card:
Routing number:

Detailed Breakdown

7 metrics
PRIMARY RESULT
Valid card number
Card Number Check
Card Network
Visa
Digits Entered
16 digits (Visa uses 13, 16 or 19)
Luhn Checksum
Passes
Security Code
CVV2: 3 digits on the back of the card
Number Shown Masked
424242••••••4242
Debit, Credit or Prepaid?
The number alone does not say. Only the issuer knows

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When to Use This Calculator

Everyday financial situations where this tool gives you fast, accurate clarity:

✍️

Catch a Typo

See at once whether a card number has a wrong digit and which digit would fix it.

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Identify the Card Network

Find out whether a number is Visa, Mastercard, American Express, Discover or another network.

🏦

Check a Routing Number

Verify the 9-digit number on a check before you send an ACH or wire transfer.

🧪

Test a Payment Form

Use the test numbers to try the checkout or form you are building.

Calculation Formula

Standard Method

Luhn checksum: starting from the rightmost digit, double every second digit, subtract 9 from any result above 9, add all the digits, and the total must be a multiple of 10. Card network by the first digits: Visa 4; Mastercard 51-55 and 2221-2720; American Express 34 and 37; Discover 6011, 644-649, 65 and 622126-622925; JCB 3528-3589; Diners Club 300-305, 36, 38 and 39; UnionPay 62. Length by network: Visa 13, 16 or 19; Mastercard 16; American Express 15; Discover 16 to 19; JCB 16 to 19; Diners Club 14 to 19. Security code: 3 digits on the back for most cards, 4 digits on the front for American Express. Routing number (3-7-1): 3 × (d1 + d4 + d7) + 7 × (d2 + d5 + d8) + 1 × (d3 + d6 + d9) must be a multiple of 10. Routing symbol (first two digits): 01-12 commercial banks, 21-32 thrift institutions (district + 20), 61-72 electronic transactions (district + 60), 80 traveler's checks. UnionPay cards are not required to pass the Luhn check. The masked number shows the first six and last four digits at most.

Benchmark Example:
The widely published Visa test number 4242 4242 4242 4242: • Network: starts with 4, so Visa • Length: 16 digits, which Visa allows • Luhn: doubling every second digit from the right and adding gives 80, a multiple of 10, so it passes • Security code: 3 digits on the back • Masked: 424242••••••4242 Change the last digit to 1 and the sum is 79: the check fails and the tool tells you the last digit should be 2. A routing number, 011000015: • 3 × (0 + 0 + 0) + 7 × (1 + 0 + 1) + 1 × (1 + 0 + 5) = 0 + 14 + 6 = 20, a multiple of 10, so the checksum passes • The first two digits, 01, are a commercial bank routing symbol for Federal Reserve District 1, Boston • Changing the last digit to 6 gives 21 and fails, and the tool shows that the last digit should be 5.

Frequently Asked Questions

7 answers

Applicable Laws & Regulatory Standards

ISO, PCI Security Standards Council & Federal Reserve Financial Services

Official Legal Reference
ISO/IEC 7812-1 — Identification cards: Numbering system and registration procedure for issuer identifiers

Defines the structure of a payment card number, the issuer identification number at the start and the Luhn check digit at the end, which are the two things this tool reads.

PCI DSS v4.0, Requirement 3.4.1 — Mask the primary account number (PAN) when displayed

Allows showing at most the BIN and the last four digits of a card number, a limit this tool respects by echoing only the first six and last four digits.

American Bankers Association (ABA) routing transit number and Federal Reserve routing symbol

Defines the 9-digit routing number, its 3-7-1 check digit and the first two digits that identify the Federal Reserve district and the type of institution.

NACHA Operating Rules — ACH Network

Govern ACH payments, which use the routing number to direct a debit or credit to the right bank, and require the receiving bank identifier to carry a valid check digit.

Legal citations and statutes are provided for consumer transparency, analytical validation, and educational reference under U.S. consumer financial regulations. This tool is not a substitute for formal legal, accounting, or tax counsel.

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