Data Source and Methodology

This tool validates card numbers based on two public standards: the Luhn Algorithm (also known as the "modulus 10" or "mod 10" algorithm) for checksum validation, and the ISO/IEC 7812 standard for identifying the card issuer via the Issuer Identification Number (IIN), which are the first 6-8 digits of the card number.

Authoritative Source: The Luhn algorithm is a public-domain algorithm published by IBM engineer Hans Peter Luhn. The IIN prefixes are managed by the American Bankers Association and standardized under ISO/IEC 7812.

All calculations are based strictly on the formulas and IIN prefix patterns defined by these public standards. This tool does not use any private databases or payment networks.

The Formula Explained: Luhn Algorithm

The Luhn algorithm is a step-by-step process used to create a checksum. This tool reverses that process to validate the number. Here is how it works:

  1. Drop the last digit: The last digit is the "check digit," which we will set aside.
  2. Reverse the remaining digits: The digits are read from right to left.
  3. Double every second digit: Starting from the new first digit (the one that was second-to-last), multiply every other digit by 2.
  4. Sum the digits: If any doubled digit is a two-digit number (e.g., 16), add its individual digits together (e.g., 1 + 6 = 7) before summing. Sum all the digits from this step.
  5. Add the check digit: Add the original "check digit" (from step 1) to this total sum.
  6. Check for validity: If the final total sum is perfectly divisible by 10 (i.e., the sum ends in a 0), the number is **valid**.

Glossary of Terms

Credit Card Number
A 13 to 19-digit number, also known as a Primary Account Number (PAN), that identifies the issuer and the cardholder account.
Luhn Algorithm (Mod 10)
A simple checksum formula used to validate identification numbers. It helps protect against accidental errors from manual data entry (typos) but is not a security feature.
Issuer Identification Number (IIN)
The first 6 to 8 digits of a card number. It identifies the card issuer (e.g., Visa, Mastercard, American Express) and allows transactions to be routed correctly.
Check Digit
The final digit of the card number, calculated using the Luhn algorithm based on the preceding digits.
CVV/CVC (Card Verification Value)
The 3 or 4-digit security code (usually on the back) used to verify "card-not-present" transactions. You should never enter this code into any tool except a secure payment form.

How It Works: A Step-by-Step Example

Let's validate the test number: 49927398716

  1. Check Digit: The check digit is 6.
  2. Remaining Digits: 4992739871
  3. Reverse: 1789372994
  4. Double every second digit:
    • (1) → 1
    • (7 * 2) → 14
    • (8) → 8
    • (9 * 2) → 18
    • (3) → 3
    • (7 * 2) → 14
    • (2) → 2
    • (9 * 2) → 18
    • (9) → 9
    • (4 * 2) → 8
  5. Sum the digits (if > 9, add its digits):
    1 + (1+4) + 8 + (1+8) + 3 + (1+4) + 2 + (1+8) + 9 + 8
    1 + 5 + 8 + 9 + 3 + 5 + 2 + 9 + 9 + 8 = 64
  6. Add check digit:
    64 + 6 = 70
  7. Final Check:
    70 % 10 = 0. Since the result is 0, the number is **Valid**.

Frequently Asked Questions

Is this credit card validator tool safe to use?

Yes. This tool is 100% safe. All validation logic runs directly in your web browser (client-side). We do not see, store, or transmit your credit card number to any server. It only performs a mathematical check and does not connect to any bank or payment network.

Can this tool check if a card has money or is active?

No. This tool only performs a mathematical check called the Luhn algorithm. It confirms that the number is formatted correctly, but it cannot check for available funds, if the card is active, or if it has been reported stolen. Only a payment processor can do that.

What is the Luhn algorithm (Mod 10 check)?

The Luhn algorithm is a simple checksum formula used to validate a variety of identification numbers, including credit card numbers. It was designed to protect against accidental errors, like typos, during manual data entry. It is not a security feature.

Why would a 'Valid' card number be declined?

A card number can be 'Valid' according to the Luhn algorithm but still be declined for many reasons, including: insufficient funds, an incorrect expiration date or CVV, the card is expired, the card has been reported lost or stolen, or the bank's fraud detection system has blocked the transaction.

Why don't you ask for the CVV or expiration date?

You should NEVER enter your CVV, PIN, or expiration date into any online tool that isn't a secure, trusted payment gateway. These details are not needed for Luhn validation, and asking for them is a major security risk.

Does this tool generate credit card numbers?

No. This tool only validates existing numbers. It does not generate or create new credit card numbers.

What do the different card prefixes (IINs) mean?

The first few digits (IIN) identify the card network. For example:

  • 4: Visa
  • 51-55: Mastercard
  • 34 or 37: American Express
  • 6011 or 65: Discover
This tool identifies the most common ones.

Tool developed by Ugo Candido. Content verified by the CalcDomain Editorial Board.
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