In this post, we are going to learn How to calculate the area of a circle in Python with some code and math modules.

### 1. Python Program to Find area of circle

To find the area of the circle we taking the circle radius input from the user using the input() method and convert the input to float using the **float()** method, **pi **has constant value so store it in variable **pi**.

- The formula to calculate area of circle is =
**πr2** - where
**π**is**pi** - r2 is
**radius * radius**

#### Python Program

```
Pi = 3.14
Redius = float(input("Enter a circle radius :"))
circle_area = Pi * Redius * Redius
print("Calculated area of a circle = %.2f" %circle_area)
```

Output

```
Enter a circle radius :12
Calculated area of a circle = 452.16
```

### 2. Python Find area of circle Using Function

We have defined a custom function cal_circle_area() with a two-parameter to find the area of a circle.

#### Python Program to calculate area of circle

```
Pi = 3.14
Redius = float(input("Enter a circle radius :"))
def cal_circle_area(Pi,radius):
return Pi * (radius*radius);
print("Calulcated Area of circle = %.3f" % cal_circle_area(Pi,Redius));
```

Output

```
Enter a circle radius :12.5
Area of circle = 490.625
```

### 3. **Math Module** to Find area of a circle in Python

Instead of custom code, we can use the inbuilt python math module to calculate the area of a circle in Python.

#### Python Program Example

```
import math
Redius = float(input("Enter a circle radius :"))
cicle_area = math.pi * Redius * Redius
print("Calulcated Area of circle = %.3f" %cicle_area);
```

Output

```
Enter a circle radius :13.5
Calulcated Area of circle = 572.555
```

### 4. Python Program to Find area of circle using circumferce

Sometimes instead of a radius, we have a circumference of the circle. The circumference is the distance around the outside of the circle. We are using an inbuilt math module to calculate the area using circumference.

- The formaula to caluculate the area of circle using
**circumferce**is =**C²⁄ 4π**. **C²**: Is the**circumferce**of circle**π**: The value of pi.

#### Python Program

```
import math
circum = float(input("Enter a circle circumference :"))
area = (circum * circum)/(4 * math.pi)
print(" calcualted area Of a Circle = %.2f" %area)
```

Output

```
Enter a circle circumference :30
calcualted area Of a Circle = 71.62
```

### 5. Find area of circle using Diameter

Sometimes we have to calculate the area of the circle from Diameter. The diameter is twice the length of the radius of the circle, we are using the math module for this.

- The formaula to calculate the area of circle using Diameter is
**Area_of_circle =π/4*D²** **π**is the value of**pi****D²**is diameter of circle =**diameter * diameter**

#### Python Program to Find area of circle using Diameter

```
import math
diameter = float(input("Enter a circle Diameter :"))
Circle_area = (math.pi/4) * (diameter * diameter)
print(" calcualted area Of a Circle = %.2f" %Circle_area)
```

Output

```
Enter a circle Diameter :5
calcualted area Of a Circle = 19.63
```

### 6. Find area and circumference diameter of circle

In this example, we are calculating the area circumference diameter of the circle by using the simple code. We are taking radius input() from the user. The formula for these are:

- Formula to find area of circle =
**pi * Redius * Redius** - Formula to find circumference of circle =
**2 * pi * Redius** - Formula to find diameter of circle =
**2*Redius**

#### Program to calculate circle area circumference diameter

```
pi = 3.14
Redius = float(input("Enter a circle radius :"))
circle_area = pi * Redius * Redius
circle_circum = 2 * pi * Redius
circle_diameter = 2*Redius
print("Calulcated Area of circle = %.3f" %circle_area)
print(" Calculate Circumference Of a Circle = %.3f" %circle_circum)
print(" Calculated Diameter Of a Circle =%.3f" % circle_diameter )
```

Output

```
Enter a circle radius :6.9
Calulcated Area of circle = 149.495
Calculate Circumference Of a Circle = 43.332
Calculated Diameter Of a Circle =13.800
```

### 7.**Math Module** to Find area circumference Diameter of circle

This is an alternative to the above code instead of using hard code pi value the python math module can be used to Find the area circumference Diameter of the circle.

#### Python Program

```
import math
Redius = float(input("Enter a circle radius :"))
circle_area = math.pi * Redius * Redius
circle_circum = 2 * math.pi * Redius
circle_diameter = 2*Redius
print('calculated area of circle:%.3f' % circle_area)
print(" Calculated circumference Of a Circle =%.3f" % circle_circum)
print(" Calculated Diameter Of a Circle =%.3f" % circle_diameter )
```

Output

```
Enter a circle radius :6.9
calculated area of circle:149.571
Calculated circumference Of a Circle =43.354
Calculated Diameter Of a Circle =13.800
```

### 8. Python Program to Find area and primeter of a circle

In this example, we are finding the Find area and perimeter of a circle by taking input from the user.

#### Python Program

```
pi = 3.14
Redius = float(input("Enter a circle radius :"))
circle_area = pi * Redius * Redius
circle_perimeter = 2 * pi * Redius
print("Calulcated Area of circle = ",circle_area)
print(" Calculated perimeter Of a Circle = ", circle_perimeter)
```

Output

```
Enter a circle radius :9.6
Calulcated Area of circle = 289.38239999999996
Calculated perimeter Of a Circle = 60.288
```

### Summary

In this post, we have learned multiple ways of how to find the area of a circle in python we can use any of the above methods as per need to calculate the area of circles in Python.