Luhn Digit Calculator

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Use DataGeneratorTools - Luhn Digit Calculator to calculate the luhn check digit for any credit or debit card.

Luhn Algorithm

Introduction

The Luhn algorithm ("modulus 10" or "mod 10" algorithm, Luhn formula) is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers (PAN) or IMEI numbers. The algorithm is specified in ISO/IEC 7812-1 and it was designed to protect against accidental errors. The Luhn algorithm will detect any single-digit error, as well as almost all transpositions of adjacent digits. It will not, however, detect transposition of the two-digit sequence 09 to 90 (or vice versa).

Steps

• From the rightmost digit, which is the check digit, moving left, double the value of every second digit;
• If the product of this doubling operation is greater than 9, then sum the digits of the products or alternatively subtract 9 from the product.
• Take the sum of all the digits.
• Multiply by 9.
• The last digit is the check digit.

Example

Initial PAN

PAN

3

7

1

4

4

9

6

3

5

3

9

8

4

3

X

Step 1 - double the values

Double values

3

14

1

8

4

18

6

6

5

6

9

16

4

6

X

Step2 - sum the digits

Sum digits

3

5

1

8

4

9

6

6

5

6

9

7

4

6

X

Step3 - sum all digits

3 + 5 + 1 + 8 + 4 + 9 + 6 + 6 + 5 + 6 + 9 + 7 + 4 + 6 = 79

Step4 - multiply by 9

79 x 9 = 711

Result

The check digit is 1.