1. What is Check Digit Calculation?

A check digit is a form of redundancy check used for error detection on identification numbers. It consists of a single digit computed from the other digits in the number.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• Digits — The numerical sequence to be validated
• Weights — The weight factors for each digit position
• mod 10 — The remainder after division by 10

Explanation: Each digit is multiplied by its corresponding weight, then summed. The check digit is the remainder when this sum is divided by 10.

3. Importance of Check Digits

Details: Check digits are crucial for detecting errors in identification numbers like credit cards, barcodes, and ID numbers. They help prevent fraud and data entry errors.

4. Using the Calculator

Tips: Enter the digits and corresponding weights (comma or space separated). Both fields must have the same number of values. Only numeric values are accepted.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between digits and weights?
A: Digits are the numbers you want to validate, weights are multipliers assigned to each digit position.

Q2: What are common weight patterns?
A: Common patterns include 1-2-1-2 (UPC), 3-1-3-1 (EAN), or alternating weights like 1-3-1-3.

Q3: What does mod 10 mean?
A: It means divide by 10 and take the remainder (e.g., 17 mod 10 = 7).

Q4: Can this calculator handle letters?
A: No, this calculator only works with numeric digits. Letters would need to be converted to numbers first.

Q5: What if my check digit is 0?
A: A check digit of 0 is valid and means the weighted sum is exactly divisible by 10.