# C++ Program to Calculate the Sum of Natural Numbers

In this post, we will learn how to calculate the sum of natural numbers using C++ Programming language.

This program asks the user to enter a maximum natural number upto which the user wants the sum. Then, it calculate the sum of natural numbers using the following approaches:

1. Using For Loop
2. Using While Loop
3. Using Do While Loop

So, without further ado, letâ€™s begin this tutorial.

Contents

## C++ Program to Calculate the Sum of Natural Numbers

```// C++ Program to Calculate the Sum of Natural Numbers
#include <iostream>
using namespace std;

int main(){
int num, sum = 0;

cout << "Enter the maximum number: ";
cin >> num;

// Calculating sum using for loop
for (int i =1; i <= num; i++){
sum = sum + i;
}

// Displaying output
cout << "Sum of natural numbers: " << sum << endl;
return 0;
}
```

OutputÂ

``````Enter the maximum number: 25
Sum of natural numbers: 325
``````

## How Does This Program Work ?

```    int num, sum = 0;
```

In this program, we have declared two integer data type variables named num and sum, where the sum variable has assigned a value of 0.

```    // Asking for input
cout << "Enter the maximum number: ";
cin >> num;
```

Now, the user is asked to enter a maximum number upto which the user wants the sum. This value gets stored in the num named variable.

```    // Calculating sum using for loop
for (int i =1; i <= num; i++){
sum = sum + i;
}
```

We initiate the for loop with the i = 1 and the value of i keeps incrementing by 1 until the value of i is less than or equal to num.

For every iteration, the sum variable becomes sum = sum + 1.

Suppose, the user enters the maximum number 3.

• Then, After the 1st iteration sum = sum + i = 0 + 1 = 1.
• After the 2nd iteration sum = sum + i = 1 + 2 = 3.
• And after the 3rd iteration, sum = sum + i = 3 + 3 = 6.

After that i > num, so the loop terminates and we get sum = 6.

```    // Displaying output
cout << "Sum of natural numbers: " << sum << endl;
```

The sum calculated in the previous step is displayed on the screen using the cout statement.

## C++ Program to Calculate the Sum of Natural Numbers Using While Loop

```// C++ Program to Calculate the Sum of Natural Numbers Using While Loop
#include <iostream>
using namespace std;

int main(){
int num, sum = 0;

cout << "Enter the maximum number: ";
cin >> num;

int i = 1;
while (i <= num){
sum = sum + i;
i++;
}

// Displaying output
cout << "Sum of natural numbers: " << sum << endl;
return 0;
}
```

Output

```Enter the maximum number: 3
Sum of natural numbers: 6
```

## C++ Program to Calculate the Sum of Natural Numbers Using Do While Loop

```// C++ Program to Calculate the Sum of Natural Numbers Using Do While Loop
#include <iostream>
using namespace std;

int main(){
int n, i = 1, sum = 0;

cout << "Enter the maximum number: ";
cin >> n;

// Calculating the sum using do-while loop
do {
sum = sum + i;
i++;
}
while (i <= n);

// Displaying output
cout << "Sum of natural numbers: " << sum << endl;
return 0;
}
```

Output

``````Enter the maximum number: 10
Sum of natural numbers: 55
``````

## Conclusion

I hope after going through this post, you understand how to calculate the sum of natural numbers using C++ Programming language.

If you have any doubt regarding the program, then contact us in the comment section. We will be delighted to assist you.