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Luhn Algorithm


The Luhn Algorithm, also known as the mod 10 algorithm, is a simple checksum formula used to validate various identification numbers such as credit card numbers. It checks the arrangement of the numbers to detect any mistakes or simple errors. The algorithm works by applying simple calculations to the digits, then predicting the checksum, and comparing it with the one written in the credit card number.


The phonetics of the keyword “Luhn Algorithm” is: /luːn ˈælɡərɪðəm/

Key Takeaways

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  1. The Luhn Algorithm, also known as the “modulus 10” or “mod 10” algorithm, is a simple checksum formula used to validate a variety of numbers, particularly credit card numbers and IMEI numbers.
  2. The algorithm works by taking a number, reverse ordering the digits, then summing up the digits whilst processing the even-indexed digits differently from the odd-indexed. If the final sum is divisible by 10, then the number is considered valid according to the Luhn algorithm.
  3. The algorithm is designed to protect against accidental errors, such as a digit mistyping. It is not designed as a measure for security against intentional errors or fraud.



The Luhn Algorithm, also known as the “modulus 10” or “mod 10” algorithm, is instrumental in the business and finance sector, primarily when dealing with credit card numbers, IMEI numbers, National Provider Identifier numbers in the US, and Canadian Social Insurance Numbers. This simple checksum formula, designed by IBM scientist Hans Peter Luhn, is critical because it helps safeguard against accidental errors or typos in numerical identification systems. By validating the authenticity of the numbers included, it significantly reduces the number or instances of frauds and operational inaccuracies. Therefore, it plays a significant role in enhancing the integrity and efficiency of financial operations.


The primary purpose of the Luhn Algorithm, also known as the “modulus 10” or “mod 10” algorithm, is to authenticate and validate a sequence of numbers such as credit card numbers, IMEI numbers, National Provider Identifier numbers in the US, and Canadian Social Insurance Numbers. It is an error-checking process, created by scientist Hans Peter Luhn, used to safeguard against typos or other mistakes in the numeric entries. By using the algorithm, companies can verify a large sequence’s accuracy of numbers without required any external reference.In the world of finance and business, the Luhn Algorithm serves a crucial function in maintaining the integrity of transactions, preventing invalid card numbers from being used for fraudulent purposes. Credit card companies use the algorithm as a simple, easy to apply, yet highly effective form of due diligence. For instance, when a customer enters their credit card information to make an online purchase, the algorithm can be used immediately to check the input for errors or inconsistencies, thus preventing fraudulent transactions and ensuring smooth, secure financial interactions.


1. Credit Card Verification: The most common use of the Luhn algorithm is in the verification of credit card numbers. This algorithm is applied by credit card issuers to determine whether a particular card number is a valid one or not, helping prevent some types of credit card fraud.2. IMEI Numbers: The International Mobile Equipment Identity (IMEI) is a unique identifier for mobile devices and also uses the Luhn algorithm for verification. IMEI numbers are used for identifying valid devices and can be used to block lost or stolen mobile phones.3. ISBN-13 Validation: The International Standard Book Number (ISBN-13), used to identify books globally, uses the Luhn algorithm in its validation process. This helps in ensuring the accuracy of data entry when recording book information in libraries, online stores, and other databases.

Frequently Asked Questions(FAQ)

What is the Luhn Algorithm?

The Luhn Algorithm, also known as the modulus 10 or mod 10 algorithm, is a simple checksum formula used to validate a variety of identification numbers, especially credit card numbers.

How does the Luhn Algorithm work?

The algorithm works by assigning each digit in the number sequence a value according to its position. From the rightmost digit, every second digit is multiplied by two. If this multiplication results in a two-digit number, the digits are added together. If not, the original number remains. Then, all values are added up to form a total. A number passes the Luhn test if the total ends in 0.

What is the purpose of the Luhn Algorithm?

The Luhn Algorithm is an error-detection method designed to quickly validate and check the integrity of certain number sequences, such as credit card numbers, IMEI numbers, and Canadian Social Insurance Numbers. It helps prevent human errors like typing mistakes.

Is the Luhn Algorithm a security method?

While the Luhn Algorithm does add a level of verification to number sequences, it is not a method for securing sensitive information. Instead, it serves as a basic check that a number sequence has been entered correctly.

Can the Luhn Algorithm detect all errors in a number sequence?

No, the Luhn Algorithm is not foolproof. While it’s good at catching single-digit errors or simple transpositions of adjacent digits, it won’t always catch more complex error patterns.

Who developed the Luhn Algorithm?

The Luhn Algorithm was created by a scientist named Hans Peter Luhn, who worked for IBM. It was patented in the U.S. in the 1960s.

Where is the Luhn Algorithm commonly used?

This algorithm is predominantly used in credit card number validation. However, it’s also used for other number sequences like Social Insurance Numbers in Canada, IMEI numbers for mobile phones, and National Provider Identifiers in the U.S health industry.

Related Finance Terms

  • Check Digit
  • Credit Card Validation
  • Modulo Operation
  • Error Detection
  • Identification Numbers

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