Software & Finance

C# - Finding Greatest Common Divisor (GCD) and Least Common Multiple (LCM)

I have given here the source code for calculating Greatest Common Divisor(GCD) and Least Common Multiple (LCM).


GCD can be found with a simple while loop by comaring the two numbers and assigning the difference to the largest number until the two numbers are equal. Once you know GCD, finding LCM is easy with the formula

LCM(a,b) = (a * b)/ GCD(a,b)


Source Code

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;


namespace ConsoleApplication1


    class Program


        static int GetGCD(int num1, int num2)


            while (num1 != num2)


                if (num1 > num2)

                    num1 = num1 - num2;


                if (num2 > num1)

                    num2 = num2 - num1;


            return num1;




        static int GetLCM(int num1, int num2)


            return (num1 * num2) / GetGCD(num1, num2);



        static void Main(string[] args)


            Console.WriteLine("C# Program for LCM and GCD");


            Console.Write("Enter First Number: ");

            int a = Convert.ToInt32(Console.ReadLine());


            Console.Write("Enter Second Number: ");

            int b = Convert.ToInt32(Console.ReadLine());


            int gcd = GetGCD(a, b);

            int lcm = GetLCM(a, b);


            Console.WriteLine("\nGCD({0,4},{1,4}) = {2,6}", a, b, gcd);

            Console.WriteLine("\nLCM({0,4},{1,4}) = {2,6}", a, b, lcm);








C# Program for LCM and GCD

Enter First Number: 10

Enter Second Number: 135


GCD(10,135) = 5

LCM(10,135) = 270



Press any key to continue . . .