1. What is the Luhn Algorithm?

The Luhn algorithm, also known as the "modulus 10" algorithm, is a simple checksum formula used to validate a variety of identification numbers, especially credit card numbers and IMEI numbers. The algorithm generates a check digit that can be used to verify the validity of the number.

2. How Does the Calculator Work?

The calculator uses the Luhn formula:

Where:

• \( sum \) — The sum calculated by the Luhn algorithm
• \( digit \) — The resulting check digit (0-9)

Calculation Steps:

1. Starting from the right, double every second digit
2. If doubling results in a number greater than 9, subtract 9
3. Sum all the digits
4. The check digit is what makes the sum a multiple of 10

3. Importance of Check Digits

Details: Check digits help prevent errors when numbers are entered manually or transmitted electronically. They can detect single-digit errors and most adjacent digit transpositions.

4. Using the Calculator

Tips: Enter the number without the check digit. The calculator will compute the correct check digit and show the complete valid number.

5. Frequently Asked Questions (FAQ)

Q1: What is the Luhn algorithm used for?
A: It's widely used in credit card numbers, IMEI numbers, various ID numbers, and other applications where error detection is important.

Q2: Does the Luhn algorithm provide security?
A: No, it's only for error detection, not security. It can't prevent malicious changes, only accidental errors.

Q3: Can the Luhn algorithm detect all errors?
A: No, it detects most but not all errors. It will catch about 90% of common transcription errors.

Q4: Why is it called modulus 10?
A: Because the check digit makes the entire number's sum divisible by 10 (sum mod 10 = 0).

Q5: What's the difference between validation and generation?
A: Validation checks if an existing number is valid, while generation creates a check digit for a new number.