Simple Calculator App in HTML CSS and JavaScript

Simple calculator App HTML CSS Javascript
Simple calculator App HTML CSS Javascript

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Are you ready to embark on an exciting journey into the world of web development? Building a simple calculator app in HTML CSS, and JavaScript is an excellent starting point.

In this comprehensive guide, we will walk you through the process step by step, from setting up your project to adding functionality and styling. By the end of this tutorial, you’ll have a fully functional calculator app that you can proudly showcase.

Setting the Stage: What You Need

Before we dive into the coding, let’s make sure you have everything you need to create your Simple Calculator App in HTML CSS, and JavaScript.

Prerequisites – Simple Calculator App in HTML CSS

To successfully build the simple calculator app in HTML CSS, you’ll need the following:

  1. HTML: This will be the structure of your app.
  2. CSS: For styling and making your calculator visually appealing.
  3. JavaScript: To add functionality and perform calculations.
  4. A code editor: Choose a code editor of your preference. Some popular options include Visual Studio Code, Sublime Text, or Atom.

Creating the Project Structure

To get started, create a new project folder on your computer. Inside this folder, create three files: index.html, style.css, and script.js.

Now that we have our project structure set up, let’s dive into each component.

HTML: Building the Structure

In this section, we’ll create the HTML structure for our calculator app. The HTML file serves as the backbone of our application.

<!DOCTYPE html>

    <title>Simple Calculator</title>
    <link rel="stylesheet" type="text/css" href="styles.css">

    <div class="calculator">
        <input type="text" id="display" disabled>
        <div class="keypad">
            <button class="operator" onclick="appendValue('/')">/</button>
            <button class="operator" onclick="appendValue('*')">x</button>
            <button onclick="appendValue('7')">7</button>
            <button onclick="appendValue('8')">8</button>
            <button onclick="appendValue('9')">9</button>
            <button class="operator" onclick="appendValue('-')">-</button>
            <button onclick="appendValue('4')">4</button>
            <button onclick="appendValue('5')">5</button>
            <button onclick="appendValue('6')">6</button>
            <button class="operator" onclick="appendValue('+')">+</button>
            <button onclick="appendValue('1')">1</button>
            <button onclick="appendValue('2')">2</button>
            <button onclick="appendValue('3')">3</button>
            <button id="clear-btn" onclick="clearDisplay()">C</button>
            <button onclick="appendValue('0')">0</button>
            <button id="calculate-btn" onclick="calculate()">=</button>

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


CSS: Adding Style simple calculator app in HTML CSS

Next, let’s style our calculator to make it visually appealing. Create a style.css file and add the following CSS code:

.calculator {
    width: 250px;
    margin: 0 auto;
    padding: 20px;
    background-color: #f0f0f0;
    box-shadow: 0px 0px 10px 0px rgba(0, 0, 0, 0.2);
    border-radius: 5px;

#display {
    width: 100%;
    height: 30px;
    margin-bottom: 10px;
    padding: 5px;

.keypad {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 10px;

button {
    width: 100%;
    height: 30px;
    font-size: 14px;

button.operator {
    background-color: #ff9933;
    color: #fff;
    font-weight: bold;

JavaScript: Adding Functionality

Now comes the exciting part – adding functionality to our calculator using JavaScript. Create a script.js file and add the following JavaScript code:

// Function to append the clicked button value to the display
function appendValue(value) {
    // Your code here

// Function to clear the display
function clearDisplay() {
    // Your code here

// Function to evaluate and display the result
function calculate() {
    // Your code here

Adding Buttons and Functionality

To complete your simple calculator app in HTML CSS, you’ll need to add buttons for digits, operators, and the equal sign in your HTML file. Attach the appropriate functions to these buttons using JavaScript. Don’t forget to style the buttons in your CSS to make them visually appealing.


Can I build a simple calculator app in HTML CSS as a beginner in web development?

Absolutely! Building a simple calculator app in HTML CSS is a great starting point for beginners. This project will help you grasp the fundamental concepts of HTML, CSS, and JavaScript.

What are LSI keywords, and why should I use them?

LSI (Latent Semantic Indexing) keywords are words or phrases related to your main keyword. Using LSI keywords in your headings and subheadings can improve SEO by making your content more contextually relevant to search engines.

Are there any resources to help me with this project?

Yes, there are numerous online tutorials and documentation available. You can also join web development communities and forums to seek help and guidance from experienced developers.

How can I make my calculator visually appealing?

You can style your calculator using CSS to change the colors, fonts, and layout. Experiment with different designs to make it visually engaging.

Is it necessary to use an external code editor?

While not mandatory, using a code editor designed for web development can significantly enhance your coding experience. They offer features like syntax highlighting, code suggestions, and debugging tools.

How can I test my calculator app?

You can test your app by opening the index.html file in a web browser. Make sure to test various scenarios to ensure your calculator functions correctly.


Congratulations! You’ve just learned how to create a simple calculator app in HTML CSS, and JavaScript. This project is a fantastic way to kick-start your web development journey. Keep practicing, and exploring advanced features, and soon you’ll be building more complex web applications.

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