C program to calculate LCM of given two numbers

In this tutorial, We are going to learn a writing program to calculate the LCM of two numbers.

Before writing a program let’s understand

What is LCM? How to calculate LCM?

LCM stands for Least Common Divisor, which is a value of two numbers that are evenly divisible by the two given numbers.

For example:

LCM of 12 and 15 is 60. Because 60 is the least number which is divided by both 12 and 15.

LCM Calculation

To calculate the LCM of numbers first find the factors of the numbers.

Here we are calculating LCM of 12 and 15.

Factors of 12 are 2 * 2 * 3

Factors of 15 are 5 * 3

Now take the common number which is in both factors and all the numbers which are not common and multiply them.

Here 3 is common and 2,2 and 5 are not common. So we are taking both and multiplying.

After multiplication 3 * 2* 2* 5 = 60.

So 60 is the LCM of 12 and 15.

Let’s see the program

C program to calculate LCM of given two numbers

#include <stdio.h>
int main() {
    int num1, num2, maxNum;
    printf("Program to find LCM of two numbers\n");
    printf("Enter the first number: ");
    scanf("%d", &num1);
    printf("Enter the second number: ");
    scanf("%d", &num2);
    maxNum = (num1 > num2) ? num1 : num2;
    while (1) {
        if (maxNum % num1 == 0 && maxNum % num2 == 0) {
            printf("The LCM of %d and %d is %d", num1, num2, maxNum);
    return 0;


Program to find LCM of two numbers
Enter the first number: 23
Enter the second number: 45
The LCM of 23 and 45 is 1035

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