C program to find sum of even numbers between 1 to n

Write a C program to input number from user and find sum of all even numbers between 1 to n. How to find sum of even numbers in a given range using loop in C programming. Logic to find sum of even numbers in a given range in C program.

Input upper limit of even number: 10

Sum of even numbers between 1 to 10: 30

Required knowledge

Basic C programming, Relational operators, For loop

Learn more – Program to check even numbers.

Logic to find sum of even numbers

Step by step descriptive logic to find sum of even numbers.

1. Input upper limit to find sum of even number. Store it in some variable say N.
2. Initialize another variable to store sum with 0 say sum = 0.
3. To find sum of even numbers we need to iterate through even numbers from 1 to n. Initialize a loop from 2 to N and increment 2 on each iteration. The loop structure should look like for(i=2; i<=N; i+=2).
4. Inside the loop body add previous value of sum with i i.e. sum = sum + i.
5. After loop print final value of sum.

Program to find sum of even numbers

/**
 * C program to print sum of all even numbers between 1 to n
 */

#include <stdio.h>

int main()
{
    int i, n, sum=0;

    /* Input upper limit from user */
    printf("Enter upper limit: ");
    scanf("%d", &n);

    for(i=2; i<=n; i+=2)
    {
        /* Add current even number to sum */
        sum += i;
    }

    printf("Sum of all even number between 1 to %d = %d", n, sum);

    return 0;
}

Note: Do not confuse with the shorthand assignment operator sum += i. It is equivalent to sum = sum + i.

Enter upper limit: 10
Sum of all even number between 1 to 10 = 30

Program to find sum of even numbers in given range

/**
 * C program to print sum of all even numbers in given range
 */

#include <stdio.h>

int main()
{
    int i, start, end, sum=0;

    /* Input lower and upper limit from user */
    printf("Enter lower limit: ");
    scanf("%d", &start);
    printf("Enter upper limit: ");
    scanf("%d", &end);


    /* If start is not even then make it even */
    if(start%2!=0)
    {
        start++;
    }

    for(i=start; i<=end; i+=2)
    {
        /* Add current even number to sum */
        sum += i;
    }

    printf("Sum of all even number between %d to %d = %d", start, end, sum);

    return 0;
}

Enter lower limit: 6
Enter upper limit: 10
Sum of all even number between 6 to 10 = 24

Happy coding 😉