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:

- Using For Loop
- Using While Loop
- 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; // Asking for input 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** nu**m 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; // Asking for input 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; // Asking for input 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.

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