# C Program to Find Circle's Area and Circumference

Updated on February 25, 2014

This tutorial will provide the source code of C Program to find the area and circumference of a circle provided we know the diameter or radius of a circle. If we are given Diameter of a circle, then we need to divide it by 2 so that we get the value of radius of circle as most of the calculations we do require radius.

The Formula for calculation of Area of Circle is :

Area of Circle = PI * R * R

While Formula for calculation of Circumference of Circle is :

Circumference of Circle = 2 * PI * R

We have already defined Pi as Floating type variable whose value is fixed as 3.14 for the calculation purposes.

## C Program Source Code to Find Area and Circumference of a Circle

```#include<stdio.h>
int main()
{
float PI=3.14,area,cirf;
printf("nEnter the radius of circle: ");
printf("nArea of circle : %f ",area);
cirf = 2 * PI * radius;
printf("nCircumference : %f ",cirf);
return(0);
}```

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## Output of Program :

```Enter radius of a circle : 1
Area of circle : 3.14
Circumference  : 6.28```

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