C++ program to find the volume of a cylinder in 3 different ways

How to find the volume of a cylinder:

In this post, we will learn learn how to find the volume of a cylinder with user input values. The formula we need to find the cylinder volume is πr^2h, where r is the radius of the cylinder, h is the height of the cylinder, and π is the mathematical constant PI.

Since π is a constant value, we need the radius and height of a cylinder to calculate its volume. The program will take these values as inputs from the user, calculate the volume and print it out.

Method 1: C++ program to find the volume of a cylinder:

The below program calculates the volume of a cylinder:

#include <iostream>
using namespace std;

int main()
{
    double height, radius, volume;
    double PI = 3.14159;

    cout << "Enter the height of the cylinder: " << endl;
    cin >> height;

    cout << "Enter the radius of the cylinder: " << endl;
    cin >> radius;

    volume = PI * radius * radius * height;

    cout << "The volume of the cylinder is: " << volume << endl;
}

Here,

The height, radius and volume are three double variables to hold the height, radius and volume of the cylinder.
PI is a double value to hold the value of π.
It asks the user to enter the height and radius of the cylinder. It reads the user input values and assigns these to the height and radius variables.
The calculated volume value is assigned to the volume variable and the last line prints its value.

If you run this program, it will print output as like below:

Enter the height of the cylinder: 
33
Enter the radius of the cylinder: 
5
The volume of the cylinder is: 2591.81

Enter the height of the cylinder: 
32
Enter the radius of the cylinder: 
22
The volume of the cylinder is: 48656.9

Method 2: C++ program to find the volume of a cylinder using predefined PI value:

In the above example, we used the π value from a predefined constant. It’s value is already defined in the cmath header file. Let’s learn how to use this value from cmath in the below example:

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    double height, radius, volume;

    cout << "Enter the height of the cylinder: " << endl;
    cin >> height;

    cout << "Enter the radius of the cylinder: " << endl;
    cin >> radius;

    volume = M_PI * radius * radius * height;

    cout << "The volume of the cylinder is: " << volume << endl;
}

As you can see here,

cmath header is included to the start of the program.
M_PI is the constant that holds the PI value. We are using it to calculate the volume.

Sample output:

Enter the height of the cylinder: 
100
Enter the radius of the cylinder: 
22
The volume of the cylinder is: 152053

Method 3: C++ program to find the volume of a cylinder using a separate function:

Let’s use a separate function to calculate the volume of the cylinder. This method will be called from main() or any other method and it will calculate and return the volume.

#include <iostream>
#include <cmath>
using namespace std;

double getVolume(double radius, double height)
{
    return M_PI * radius * radius * height;
}

int main()
{
    double height, radius, volume;

    cout << "Enter the height of the cylinder: " << endl;
    cin >> height;

    cout << "Enter the radius of the cylinder: " << endl;
    cin >> radius;

    volume = getVolume(radius, height);

    cout << "The volume of the cylinder is: " << volume << endl;
}

Here,

getVolume function calculates the volume. It takes the radius and height of the cylinder as parameters and returns the calculated volume.
The returned value is assigned to the double value volume in the main function.

You will get similar results.

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Updated on 24 Aug 2022

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