**Summary:** In this programming example, we will learn different ways to calculate the factorial of a number in C++.

Factorial of any positive integer n denoted by **n!** is the product of all positive integers less than or equal to n.

i.e. n! = n×(n-1)×(n-2)×(n-3)×⋯×3×2×1.

There are different ways to find factorial of a number in C++. Let’s see the example of each of them.

## Method 1: Factorial using Loop

```
#include <iostream>
using namespace std;
int main() {
int n;
unsigned long long factorial= 1;
cout << "Enter a number \n";
cin >> n;
for(int i=n; i>=1; i--){
factorial = factorial*i;
}
cout << "Factorial of " << n << " is " << factorial;
return 0;
}
```

**Output**

`Enter a number`

5

Factorial of 5 is 120

5

Factorial of 5 is 120

In this method, we loop from n to 1 in decreasing order and simultaneously multiply each number with the` factorial`

variable.

The final value of `factorial`

is the product of all numbers from n to 1 i.e. factorial of n.

The factorial of a number is always positive and could exceed the range of `int`

in C++, that’s why we used the `unsigned long long`

type to store the factorial value.

## Method 2: Factorial using Function

```
#include <iostream>
using namespace std;
unsigned long long findFactorial(int n){
unsigned long long factorial= 1;
for(int i=n; i>=1; i--){
factorial = factorial*i;
}
return factorial;
}
int main() {
int n;
cout << "Enter a number \n";
cin >> n;
cout << "Factorial of " << n << " is " << findFactorial(n);
return 0;
}
```

**Output**

`Enter a number`

6

Factorial of 6 is 720

6

Factorial of 6 is 720

This method is similar to the above discussed method but incorporated using a function.

The function using loop algorithm calculates and returns the factorial of the number `n`

.

## Method 3: Factorial using Recursion

```
#include <iostream>
using namespace std;
//Recursive Function
unsigned long long factorial(int n){
if(n==0 || n==1)
return 1;
return n*factorial(n-1);
}
int main() {
int n;
cout << "Enter a number \n";
cin >> n;
cout << "Factorial of " << n << " is " << factorial(n);
return 0;
}
```

**Output**

`Enter a number`

7

Factorial of 7 is 5040

7

Factorial of 7 is 5040

In this program, `factorial(int n)`

is a recursive method with a base condition of `n==1 || n==0`

.

If the base condition is not satisfied then we multiply the value `n`

with the next recursive call i.e. `factorial(n-1)`

.

The factorial of `n`

is returned back to the `main`

function at the end of the recursion.

In this tutorial, we learned to calculate factorial of a number in C++.