BMI Calculator in C++ | Basics of C++ - Software Development PDF Download

Introduction

A Body Mass Index (BMI) calculator helps determine whether a person is underweight, normal weight, overweight, or obese based on their height and weight. In this project, we will create a simple BMI calculator using C++. The program will take user input, calculate BMI, and categorize the result.

Understanding BMI Calculation

The formula for calculating BMI is:
However, if the weight is provided in pounds (lbs) and height in inches (in), we use:

Project Breakdown

This project involves:

• Taking user input for name, weight (lbs), and height (inches).
• Calculating BMI using the formula.
• Categorizing the BMI result.
• Displaying the output in a user-friendly format.

Code for the BMI Calculator in C++

#include <iostream>
#include <string>
using namespace std;
int main() {
    // Variables for user input
    string name;
    double weight, height, BMI;

    // Taking user input
    cout << "Enter your name: ";
    getline(cin, name);
    cout << "Enter your weight in pounds: ";
    cin >> weight;
    cout << "Enter your height in inches: ";
    cin >> height;

    // BMI Calculation
    BMI = (weight * 703) / (height * height);

    // Displaying the BMI value
    cout << "\n" << name << ", your BMI is: " << BMI << endl;

    // Categorizing BMI
    if (BMI > 0) {
        if (BMI < 18.5)
            cout << "You are underweight." << endl;
        else if (BMI <= 24.9)
            cout << "You have a normal weight." << endl;
        else if (BMI < 29.9)
           cout << "You are overweight. Consider a healthy diet and exercise." << endl;
        else if (BMI < 34.9)
            cout << "You are obese." << endl;

        else if (BMI < 39.9)
            cout << "You are severely obese." << endl;
        else
            cout << "You are morbidly obese." << endl;
    } else {
        cout << "Please enter valid inputs." << endl;
    }
    return 0;
}

Understanding the Code

1. Importing Libraries

#include <iostream>
#include <string>
iostream: Enables input and output operations.
string: Allows us to use string variables for handling names.

2. Declaring Variables and Taking Input

string name;
double weight, height, BMI;
name: Stores the user's name.
weight: Stores the user's weight in pounds.
height: Stores the user's height in inches.
BMI: Stores the calculated BMI.
User input is taken using:
cout << "Enter your name: ";
getline(cin, name);
cout << "Enter your weight in pounds: ";
cin >> weight;
cout << "Enter your height in inches: ";
cin >> height;
getline(cin, name): Reads the full name (including spaces).
cin >> weight; cin >> height;: Reads numerical inputs.

3. Calculating BMI
BMI = (weight * 703) / (height * height);
This formula converts weight and height into BMI.

4. Displaying BMI and Categorizing the Result
if (BMI > 0) {
    if (BMI < 18.5)
        cout << "You are underweight." << endl;
    else if (BMI <= 24.9)
        cout << "You have a normal weight." << endl;
    else if (BMI < 29.9)
        cout << "You are overweight. Consider a healthy diet and exercise." << endl;
    else if (BMI < 34.9)
        cout << "You are obese." << endl;
    else if (BMI < 39.9)
        cout << "You are severely obese." << endl;
    else
        cout << "You are morbidly obese." << endl;
} else {
    cout << "Please enter valid inputs." << endl;
}

• This checks the BMI value and categorizes the user's weight status accordingly.
• The program ensures the input values are valid.

How to Run the BMI Calculator

1. Open a C++ Compiler

• Use GCC, Visual Studio Code, or an online C++ compiler.

2. Copy and Paste the Code

3. Compile and Run the Program

If using a command-line compiler, type:
g++ bmi_calculator.cpp -o bmi_calculator

• ./bmi_calculator

4. Enter Your Details
Provide your name, weight (lbs), and height (inches).

5. Get Your BMI Result
The program will display your BMI and weight category.

Possible Improvements

• Allow user to input weight in kilograms and height in meters.
• Add a feature to calculate Ideal Body Weight (IBW).
• Improve user interaction with a graphical interface.
• Allow multiple calculations in a loop.

Conclusion

This simple BMI calculator demonstrates how to take user input, perform calculations, and display meaningful results in C++. It is an excellent beginner-friendly project for learning basic I/O operations, conditional statements, and arithmetic calculations.