Luhn Algorithm Calculator

Created By : Vinay Kumar Prajapati

Reviewed By : Phani Ponnapalli

Last Updated : May 07, 2025

This Luhn Algorithm Calculator is a free online tool that calculates the correct check digit for any number entered by the user in the given input section and displays the result within a fraction of seconds. This user-friendly mathematical tool is helpful in validating the numbers and finding check digit with the help of the Luhn checksum algorithm.

Luhn Algorithm (Mod 10) Calculator: It is quite an easy and simple to use tool to find out the appropriate check digit of the given set of data. Users can simply avail the output in just a fraction of seconds to perform the lengthy calculations by utilising our free online Calculator. Let's check more information about the calculator and the whole concept from this page. Here, you can find the complete details along with a convenient Luhn Algorithm Calculator.

Luhn Algorithm: Definition

The Luhn algorithm or the Modulus 10 is an algorithm to check the given set of numbers and whether they are aligned or contain an error. After the set of rules of the algorithm has been applied to the set of sequences & answer of modulus 10 comes as 0, then the sequence can be accepted as valid as per the Luhn algorithm. The Luhn algorithm is most commonly employed to check different ID numbers like credit cards, and different ID card numbers.

How does the Luhn Algorithm Work?

The Luhn algorithm is applied to the credit card numbers using a given set of rules. After all the calculations & evaluation of the final results, if it is considered as expected results, then the credit card no is considered valid.

Step by Step Explanation of Calculating the Luhn Check Digit

  • Take the sequence of numbers to check using the Luhn algorithm.
  • Write the numbers sequentially. Now, starting from left to right, & from the second digit, double the digit.
  • Moving to the left, double every second number (or numbers in even places).
  • If you get 2 digit numbers, after doubling then add the 2 digits to form a single-digit number.
  • Now add all the numbers in a sequence.
  • Divide the number by mod 10. If the answer is zero then the sequence is said to be valid & can be used.

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Example: 

Check if the number is valid using the Luhn algorithm. The number is 60071849889234.

Solution:

Write the number in tabular form.

6

0

0

7

1

8

4

9

8

2

3

4

Starting from left to right, & from the second digit, double the digit.

6 × 2

0

0 × 2

7

1 × 2

8

4 × 2

9

8 × 2

2

3 × 2

4

If 2 digit numbers, after doubling then add the 2 digits to form a single-digit number.

1+2

0

0

7

2

8

8

9

1+6

2

6

4

3

0

0

7

2

8

8

9

7

2

6

4

Add all the numbers in a sequence, & take modulus 10.

Total = 3+0+0+7+2+8+8+9+7+2+6+4 = 56

56 mod 10 = 1

The answer is 1, so the given sequence is not valid according to the Luhn algorithm.

To make this sequence valid, we can change the last number to 8.

FAQs on Testing a Number with Luhn Validation Using Luhn Algorithm Calculator

1. What is mod10?

The Luhn formula or Luhn algorithm is known as modulus 10 or mod 10 algorithm.

2. Does the Visa use the Luhn algorithm?

Luhn is known because Visa, American Express (AMEX), MasterCard, and all credit cards use it.

3. What is the Luhn formula in IMEI?

The Luhn formula is a simple checksum formula that is used in the validation of IMEI numbers.

4. What does Luhn check fail in mobile phones mean?

It means that the IMEI entered is not valid or the user has entered it wrong.