Simple Calculator in React Js

React Js Calculator: A calculator is a handy electronic tool that helps us do math problems like adding, subtracting, multiplying, and dividing numbers really fast.

It has buttons with numbers and signs like + and -, and when we press those buttons in the right order, the calculator shows us the answer on a screen. It’s like having a math helper that makes tricky math easier.

So In this tutorial, We will learn to create a React simple calculator with the following features –

  • Display Area: A space to see your numbers and calculations.
  • Number Buttons: Buttons with numbers (0-9) for input.
  • Operator Buttons: Symbols (+, -, *, /) for choosing the calculation.
  • Equal Button: Press to get the calculation result.
  • Clear Button: Clears entered numbers.
  • Math Operations: Basic math like add, subtract, etc.
  • Styling: Designed using Bootstrap 5 for a clean look.
  • React Component: Built using React.js for interactivity.
  • Functionality: Buttons work to input, operate, and display.
  • Usage: Solves simple math problems fast.

Steps to Create Calculator Using Function Component

1. Set Up Basic Configuration

First of all, You must set up the following basic configuration –

2. Create Calculator Directory

After creating the React App, You will get the default directory structure. Now, Create a calculator directory like –

    |__ Calculator/
    |    |__ Calculator.css
    |    |__ Calculator.js
    |__ App.js
    |__ index.js

Default React App contains more folders & files but  I have shown here only required one.

3. Create a Calculator component

Now, Create a file Calculator.js inside the ‘Calculator’ folder and define a function component named ‘Calculator’ for making a simple calculator system.

File Name – Calculator.js

import React, { useState } from 'react';
import 'bootstrap/dist/css/bootstrap.min.css';
import "./Calculator.css"

function Calculator() {
  const [resultValue, setResultValue] = useState('0');
  const handleBtnClick = (buttonValue) => {
    if (resultValue === '0') {
    } else {
      setResultValue(resultValue + buttonValue);

  const handleCalculate = () => {
    try {
    } catch (error) {

  const handleClear = () => {

  return (
    <div className="container mt-5">
      <div className='row'>
        <div className='col-sm-4'>
        <div className="calculator">
        <h4>React Simple Calculator</h4>
        <input type="text" className="form-control mb-3" value={resultValue} readOnly />
        <div className="input-group">
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('7')}>7</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('8')}>8</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('9')}>9</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('+')}>+</button>
        <div className="input-group">
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('4')}>4</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('5')}>5</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('6')}>6</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('-')}>-</button>
        <div className="input-group">
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('1')}>1</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('2')}>2</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('3')}>3</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('*')}>*</button>
        <div className="input-group">
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('0')}>0</button>
          <button className="btn btn-outline-primary" onClick={handleClear}>C</button>
          <button className="btn btn-outline-primary" onClick={handleCalculate}>=</button>
          <button className="btn btn-outline-primary" onClick={() => handleBtnClick('/')}>/</button>
        <div className='col-sm-8'>


export default Calculator;

Steps to write code:

Sure, here’s an explanation of the code line by line in a pointwise manner:

  • Import React and the `useState` hook from the ‘react’ library.
  • Import the Bootstrap CSS and a custom CSS file named “Calculator.css”.
  • Define a functional component named `Calculator`.
  • Inside the component, set up a state variable `resultValue` using the `useState` hook, initialized to `’0’`.
  • Define a function `handleBtnClick` that takes a `buttonValue` parameter and updates `resultValue` based on the button clicked.
  • If the current `resultValue` is `’0’`, update it with the `buttonValue`; otherwise, concatenate the `buttonValue` to the existing `resultValue`.
  • Define a function `handleCalculate` that calculates the result of the expression in `resultValue` using the `eval` function.
  • If the evaluation succeeds, convert the result to a string and update `resultValue`. If there’s an error during evaluation, set `resultValue` to `’Error’`.
  • Define a function `handleClear` that resets `resultValue` to `’0’`.
  • Return JSX (React code) to render the calculator interface.
  • Use the Bootstrap grid system to structure the layout: a container with rows and columns.
  • Inside the component, create a title heading and an input field to display the `resultValue`, which is bound to the input’s value.
  • Create a series of rows of buttons, each containing a group of four buttons for digits and operators.
  • Assign click handlers to the buttons using inline arrow functions to call `handleBtnClick` with the respective value when clicked.
  • The buttons display digits 0-9 and operators +, -, *, and /.
  • Include buttons for calculation (`=`) and clearing (`C`), which have their own specific handlers.
  • The component returns the entire layout of the calculator interface, with buttons organized in a grid.
  • The component is exported as the default export of the module, allowing it to be used in other parts of the application.

4.  Design a Calculator using CSS

Now, Create a folder named ‘Calculator.css’ within the ‘Calculator’ folder.

File Name – Calculator.css

.calculator button{
    width: 60px;
    height: 60px;
    border-radius: 0px;
    margin: 5px 10px;
    font-weight: bold;
    font-size: 20px;
.calculator .input-group{
    width: 81%;
    display: inline-block;
.calculator input[type="text"]{
    border-radius: 0px;
    height: 46px;
    display: inline-block;
    width: 75%;
    margin: 0px 10px

.calculator h3{
    position: relative;
    left: 17px;
    text-decoration: underline;
    margin-bottom: 22px;
    color: #0e7bf2;


.calculator button:

  • Styles buttons within the calculator.
  • Sets size, square corners, margins, bold text, and font size.

.calculator .input-group:

  • Styles input groups within the calculator.
  • Adjusts width and makes them inline blocks.

.calculator input[type=”text”]:

  • Styles text input within the calculator
  • Sets size, square corners, margins, and width.

.calculator h3:

  • Styles heading within the calculator.
  • Adjusts position, adds underline, margin, and changes text color.

5.  Load a Calculator component

  • It imports the `Calculator` component from the “./calculator/Calculator” path.
  • The `App` component returns the `Calculator` component, which is intended to render a calculator interface.
  • The `App` component is exported as the default export of the module.

File Name – App.js

import Calculator from "./calculator/Calculator";
function App() {
  return (
    <Calculator />

export default App;

6.  Display Calculator in Web Browser

To display the calculator in a web browser, first run the following command in your terminal.

npm start

After that, open the following URL in your web browser to see the calculator