# Circumference Of Circle C++ Example Program

## Definition

When a circle's diameter is 1, its circumference is π. When a circle's radius is 1—called a unit circle—its circumference is 2π.

## Formula

The circumference of a circle is written

π = C / d

Or, equivalently, as the ratio of the circumference to twice the radius. The above formula can be rearranged to solve for the circumference:

`C = π * d = 2π * r`

here,

```r = Radius
π = ~3.14```

## Circumference Of Circle Example Program

``````/*## Circumference Of Circle In C++*/
/*## Calculation C++ Programs, Datatype C++ Programs, Basic C++ Programs*/

#include <iostream>
#include<conio.h>
#include<stdlib.h>

using namespace std;

float PI = 3.14;

int main() {
// Declare Variables

cout << "Simple C++ Program : Circumference Of Circle\n";
cout << "\nEnter the radius of Circle : ";

ci = 2 * PI * radius;

cout << "\nCircumference of Circle : " << ci;

getch();
return (0);
}``````

## Sample Output

``````Simple C++ Program : Circumference Of Circle

Enter the radius of Circle : 5

Circumference of Circle : 31.4``````