Building a BMI Calculator with HTML, CSS, and JavaScript

Hello, fellow developers! Today, I’m excited to share a project that I recently worked on: a BMI (Body Mass Index) Calculator. This simple web application helps users calculate their BMI based on their height and weight, offering a straightforward way to assess their health status. Let's dive into the details of the project and how it was built!

Project Overview

The BMI Calculator is a user-friendly tool that allows users to input their height (in centimeters) and weight (in kilograms). With just a click of a button, the application computes the BMI and displays the corresponding health category, such as Underweight, Normal weight, Overweight, or Obesity.

Features

• User Input: Users can enter their height and weight directly into the input fields.
• BMI Calculation: The application calculates the BMI using the standard formula.
• Health Category: Based on the calculated BMI, the app provides a relevant health category.
• Responsive Design: The calculator is designed to be responsive, ensuring a smooth experience across different devices.

Technologies Used

• HTML: Structures the content of the webpage.
• CSS: Styles the application, providing a clean and modern look.
• JavaScript: Handles the BMI calculation and updates the DOM to display results.

Project Structure

Here’s a quick overview of the project structure:

BMI-Calculator/
├── index.html
├── style.css
└── script.js

Code Explanation

Let’s take a closer look at the code that powers the BMI Calculator.

HTML

The HTML provides the basic structure of the calculator, including input fields for height and weight, a button to trigger the calculation, and a section to display the result.

    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>BMI Calculator</title>
    <link rel="stylesheet" href="./style.css">
    <script src="./script.js" defer></script>


    <div class="header">
        <h1 id="BMI-Calculator">BMI Calculator</h1>
    </div>
    <div class="container">
        <h1 id="Body-Mass-Index-BMI">Body Mass Index (BMI)</h1>
        Your Height (cm):
        <input type="number" class="input" id="height" value="180" placeholder="Enter your height in cm">
        Your Weight (kg):
        <input type="number" class="input" id="weight" value="80" placeholder="Enter your weight in kg">
        <button class="btn" id="btn">Compute BMI</button>
        <input disabled type="text" class="input" id="bmi-result">
        <h4 class="info-text">Weight Condition: <span id="weight-condition"></span>
</h4>
    </div>
    <div class="footer">
        <p>Made with ❤️ by Abhishek Gurjar</p>
    </div>

CSS

The CSS styles the page to make it visually appealing and easy to use. It features a modern, clean design with responsive elements.

body {
    margin: 0;
    background: linear-gradient(to left bottom, lightgreen, lightblue);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    justify-content: center;
    align-items: center;
    font-family: 'Courier New', Courier, monospace;
}

.container {
    background: rgba(255, 255, 255, 0.3);
    padding: 20px;
    display: flex;
    flex-direction: column;
    border-radius: 5px;
    box-shadow: 0 10px 10px rgba(0, 0, 0, 0.3);
    margin: 5px;
}

.heading {
    font-size: 30px;
}

.input {
    padding: 10px 20px;
    font-size: 18px;
    background: rgba(255, 255, 255, 0.4);
    border-color: rgba(255, 255, 255, 0.5);
    margin: 10px;
}

.btn {
    background-color: lightgreen;
    border: none;
    padding: 10px 20px;
    border-radius: 5px;
    margin: 10px;
    font-size: 20px;
    box-shadow: 0 0 4px rgba(0, 0, 0, 0.3);
    cursor: pointer;
}

.btn:hover {
    box-shadow: 0 0 8px rgba(0, 0, 0, 0.3);
    transition: all 300ms ease;
}

.info-text {
    font-size: 20px;
    font-weight: 500;
}

.header {
    margin: 30px;
    text-align: center;
}

.footer {
    margin: 20px;
    text-align: center;
}

JavaScript

The JavaScript handles the core functionality of the application—calculating the BMI based on the user’s input and updating the webpage with the results.

const btnE1 = document.getElementById("btn");
const resultE1 = document.getElementById("bmi-result");
const weightConditionE1 = document.getElementById("weight-condition");
const heightE1 = document.getElementById("height");
const weightE1 = document.getElementById("weight");

function calculateBMI() {
    const height = heightE1.value / 100;
    const weight = weightE1.value;
    const bmiValue = weight / (height * height);

    resultE1.value = bmiValue.toFixed(2);

    if (bmiValue = 18.5 && bmiValue = 25 && bmiValue  30) {
        weightConditionE1.innerText = "Obesity";
    }
}

btnE1.addEventListener("click", calculateBMI);

Live Demo

You can try out the BMI Calculator live here.

Conclusion

Building this BMI Calculator was a rewarding experience that enhanced my skills in HTML, CSS, and JavaScript. The project showcases how a simple idea can be turned into a practical tool that users can benefit from. Whether you're looking to build a similar project or just exploring web development, I hope this tutorial helps you on your journey. Happy coding!

Author

• Abhishek Gurjar
  • GitHub Profile

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