BMI Calculator using HTML, CSS and JavaScript - Coding Torque

Welcome to Coding Torque. In this blog, we are going to create a BMI Calculator using HTML, CSS & JavaScript. You should create this project if you are a beginner and learning JavaScript. This project simply takes height and weight as input and returns BMI as output.

Before we start, here are some JavaScript Games you might like to create:

1. Snake Game using JavaScript

2. 2D Bouncing Ball Game using JavaScript

3. Rock Paper Scissor Game using JavaScript

4. Tic Tac Toe Game using JavaScript

5. Whack a Mole Game using JavaScript

I would recommend you don’t just copy and paste the code, just look at the code and type by understanding it.

HTML Code

Starter Template

<!doctype html>
<html lang="en">

<head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <!-- CSS -->
    <link rel="stylesheet" href="style.css">

    <title>BMI Calculator using JavaScript with Source Code - @code.scientist x @codingtorque</title>
</head>

<body>
    <!-- Further code here -->

    <script src="script.js"></script>
</body>

</html>

Paste the below code in your `<body>` tag

<div class="container">
    <h2 style="text-align: center;">BMI Calculator</h2>
    <form>
        <p class="inputs">
            <label>Height (CM): </label>
            <input type="number" id="height" min="1">
        </p>
        <p class="inputs">
            <label>Weight (KG): </label>
            <input type="number" id="weight" min="1">
        </p>

        <button class="calcBtn">Calculate</button>
        <div style="margin-top: 20px;">Your BMI is: <p id="results"></p>
        </div>
        <p id="message"></p>

    </form>
</div>

Output Till Now

CSS Code

Create a file style.css and paste the code below.

@import url("https://fonts.googleapis.com/css2?family=Poppins&family=Potta+One&display=swap");

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Poppins", sans-serif;
}

body {
  display: flex;
  align-items: center;
  justify-content: center;
  background: #0f172a;
}

.container {
  width: 22rem;
  margin-top: 8rem;
  background-color: white;
  border-radius: 10px;
  padding: 30px;
}

.inputs {
  display: flex;
  flex-direction: column;
  margin: 15px 0;
}

.inputs input {
  outline: none;
  height: 30px;
}

#results {
  font-size: 20px;
  text-align: center;
  color: blue;
}

.calcBtn {
  width: 100%;
  padding: 8px 0;
  margin-top: 10px;
  border-radius: 5px;
  border-style: none;
  background: #2563eb;
  color: #fff;
  cursor: pointer;
  font-size: 20px;
}

#message {
  text-align: center;
}

Output Till Now

JavaScript Code

Create a file script.js and paste the code below.

const form = document.querySelector('form');

form.addEventListener('submit', function (e) {
    e.preventDefault();

    const height = parseInt(document.querySelector('#height').value);
    const weight = parseInt(document.querySelector('#weight').value);
    const results = document.querySelector('#results');
    const message = document.querySelector('#message');

    if ((height === '') || (height < 0) || (isNaN(height))) {
        //NaN !== NaN
        results.innerHTML = "Please provide a valid height";

    } else if (weight === '' || weight < 0 || isNaN(weight)) {
        results.innerHTML = "Please provide a valid weight";
    } else {
        // Calculate BMI
        const bmi = (weight / ((height * height) / 10000)).toFixed(2);
        // Display the results
        results.innerHTML = `<span>${bmi}</span>`

        // Display End Message
        if (bmi < 18.6) {
            message.innerHTML = "You are underweight";
        } else if (bmi > 18.6 && bmi < 24.9) {
            message.innerHTML = "Normal"
        } else if (bmi > 24.9) {
            message.innerHTML = "You are Overweight"
        }
    }
});

Written by: Piyush Patil

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Hope you find this post helpful💖