Python program to find area of circle

In this post, you will learn about different Python programs to find the area of the circle. As we all know, the area of the circle is the measure of the space or region enclosed inside the circle. In geometry, the area enclosed by a circle of radius r is πr². Here is the simple formula for calculating the area of the circle.

Area = pi * r2

Algorithm

1. Define a function to calculate area
2. Set PI as constant and initialize to 3.147
3. Use the formula of the Area = πr².
3. Take input of radius from the user
4. Pass radius in the function
5. Print the result

Python program to find area of circle using radius

If we know the radius of a circle, then we can easily calculate the area using the formula: A=πr². Here is the simple Python program to calculate the area of a circle using the radius.

# program to calculate
# area of circle
def area_of_circle(r): 
    PI = 3.142
    return PI * (r*r); 
  
# get user input
radius = float(input("Enter the radius: "))

# print area of circle
print("Area is %.6f" % area_of_circle(radius));

Output of the above code-

Enter the radius: 10
Area is 314.200000

Python program to find area of circle using diameter

Diameter is the distance across the circle passing through the centre. We can also calculate the area of the circle if we know the diameter. Either, we can divide the diameter by 2 and calculate the area using the above process, like this.

# Program to calculate area of circle
 
def area_of_circle(r): 
    PI = 3.142
    return PI * (r*r); 
  
# get user input
diameter = float(input("Enter the diameter of a circle: "))
radius = diameter / 2

# print area of circle
print("Area is %.6f" % area_of_circle(radius));

Output of the above code-

Enter the diameter of a circle: 53
Area is 2206.469500

Or, we can use the following formula to calculate the area of the circle using diameter.

A=π/4*D²

Here is the program to calculate the area of the circle using the diameter. For this, we first imported the math module and then used the direct formula to calculate the area of the circle.

# Program to calculate area of circle

import math

diameter = float(input("Enter the diameter of a circle: "))
area = (math.pi/4) * (diameter * diameter)

print("Area of circle is %.2f" %area);

Output of the above code -

Enter the diameter of a circle: 23
Area of circle is 415.48

Python program to find area of circle using circumference

The circle's circumference is the distance around the circle. We can easily calculate the area of a circle if we know the circumference using the formula A= C²⁄ 4π, where C is the circumference. The following program demonstrates this.

# Program to calculate area of circle

import math

circumference = float(input("Enter the circumference of a circle: "))
area = (circumference * circumference)/(4 * math.pi)

print("Area of circle is %.2f" %area);