How to Find Square Root in Javascript

In this tutorial, you will learn how to find square root in javascript. The square root is the number which when multiplied by itself, gives the original number. For example, 3 is the square root of 9, as 3 × 3 = 9.

Calculating the square root can be tricky if the value is coming from an input field because the value present in the input field is of string type. So first, we have to convert it into a number type using the Number() method and then do the calculation.

To calculate a square root of a number, we can make use of the Math object.  This object contains a lot of methods and properties which can help us in various mathematical operations such as square root. This object contains the sqrt() method which will take a number as a parameter and returns its square root.

In the following example, we have an input field in which we will enter a random number. Upon click of a button, we will get its square root and display that on the screen.  Please have a look over the code example and the steps given below.


  • We have 4 elements in the HTML file (div, input, button, and h1). The div element with a class of container is just a wrapper for the rest of the elements.
  • The innerText for the button element is “Square Root” and for the h1 element, it is “Result”.
  • We have done some basic styling using CSS and added the link to our style.css stylesheet inside the head element.
  • We have also included our javascript file script.js with a script tag at the bottom.
<!DOCTYPE html>
<html lang="en">

  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <link rel="stylesheet" href="style.css">


  <div class="container">
    <input type="number" placeholder="Enter Number">
    <button>Square Root</button>

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

.container {        
    text-align: center;

button {
  margin-top: 10px;
  padding: 10px 20px;

input {
  display: block;  
  margin: 10px auto;
  padding: 10px 20px;

input[type=number]::-webkit-outer-spin-button { 
  -webkit-appearance: none; 
  margin: 0; 


  • We have selected the input element, button element, and h1 element using the document.querySelector() method and stored them in input, btnSqrt, and output variables respectively.
  • We have attached a click event listener to the button element.
  • In the event handler function, we are passing the value of the input element to the Number() method and storing the number in the num variable.
  • We are calling sqrt() method to get the square root of num and storing it in the result variable.
  • We only want the result to be up to 2 decimal places and that is why we are using the toFixed() method and passing 2 as a parameter.
  • We are displaying the result in the h1 element using the innerText property.
let input = document.querySelector("input");
let btnSqrt = document.querySelector("button");
let output = document.querySelector("h1");

btnSqrt.addEventListener("click", () => {
  let num = Number(input.value);
  let result = Math.sqrt(num);
  result = result.toFixed(2);
  output.innerText = result;