In this post, we will learn **how to find the factorial of a number using C++** Programming language. But before that, let’s learn about factorials.

The **factorial of a number** is the product of all integers from **1** to that number. For example, the factorial of **5** is **5!** = **5 x 4 x 3 x 2 x 1 = 120**.

We will calculate the factorial of a number entered by the user using the following approaches:

- Using For Loop
- Using While Loop

So, without further ado, let’s begin this tutorial.

**C++ Program to Find Factorial of a Number**

// C++ Program to Find Factorial of a Number #include <iostream> using namespace std; int main(){ int num, fact = 1; // Asking for input cout << "Enter a number to find the factorial: "; cin >> num; // Finding factorial of a number for (int i = 1; i <= num; i++){ fact = fact * i; } // Displaying output cout << "Factorial of " << num << " is: " << fact << endl; return 0; }

**Output**

```
Enter a number to find the factorial: 4
Factorial of 4 is: 24
```

**How Does This Program Work?**

int num, fact = 1;

In this program, we have declared two integer data type variables named **num** and **fact**. The **fact** variable has assigned a value of **1**.

// Asking for input cout << "Enter a number to find the factorial: "; cin >> num;

The user is asked to enter a number. The entered value gets stored in the **num** named variable.

// Finding factorial of a number for (int i = 1; i <= num; i++){ fact = fact * i; }

We use a **for loop** to calculate the factorial of the entered number. Suppose the user enters a number such that **num = 4**.

Now, to find the factorial of **4!**, we perform:

**1st For Loop Iteration:**for (int i = 1; i <= 4; i++)- fact = fact * i = 1 * 1 = 1.

**2nd For Loop Iteration:**for (int i = 2; i <= 4; i++)- fact = fact * i = 1 * 2 = 2.

**3rd For Loop Iteration:**for (int i = 3; i <= 4; i++)- fact = fact * i = 2 * 3 = 6.

**4th For Loop Iteration:**for (int i = 4; i <= 4; i++)- fact = fact * i = 4 * 6 = 24.

**5th For Loop Iteration:** for (int i = 5; i <= 4; i++), here the condition is** False**, so the loop **terminates** and we get **fact = 24**.

// Displaying output cout << "Factorial of " << num << " is: " << fact << endl;

The factorial of the entered number is displayed on the screen using the **cout** statement.

**C++ Program to Find Factorial of a Number Using While Loop**

// C++ Program to Find Factorial of a Number Using While Loop #include <iostream> using namespace std; int main(){ int num, i = 1, fact = 1; // Asking for input cout << "Enter a number: "; cin >> num; // Calculating factorial using while loop while (i <= num){ fact = fact * i; i++; } // Displaying output cout << "The factorial of " << num << " is: " << fact << endl; return 0; }

**Output**

```
Enter a number: 6
The factorial of 6 is: 720
```

**Conclusion**

I hope after going through this post, you understand **how to find the factorial of a number using C++** Programming language.

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

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