9+ JavaScript Programs to Calculate Area of a Circle

This post contains a total of 9+ JavaScript Program Examples with Source Code to Calculate the Area of a Circle. All these Circle Area Calculator programs are made using JavaScript.

You can use the source code of these examples with credits to the original owner.

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JavaScript Programs to Calculate Area of Circle

1. By LynTon

Made by LynTon. Simple Circle Area Calculator. Source

JavaScript Circle Area Calculator by LynTon
<!DOCTYPE HTML>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title></title>
    <style>
        body {
            text-align: center;
            background-color: #AAFFFF;
        }
        
        #heading {
            text-decoration: underline;
        }
    </style>
</head>
<body>
    <h1 id="heading">Circle Area Calculator</h1>
    
	<input id="radius" type="number" name="radius" placeholder="Enter radius here...">
	<input type="button" onclick="calculate()" value="Calculate area">
	<p>Area: <span id="area">???</span></p>
	
	<script>
	    function calculate() {
	        let r = Number(document.getElementById("radius").value);
	        document.getElementById("area").textContent = `${(Math.PI * (r * r)).toFixed(2)} (2dp)`;
	    }
	</script>
</body>
</html>

2. By Manual

Made by Manual. JavaScript Program to Find the Area of a Circle, it uses the Prompt to take input. Source

10
The area of the circle is 314
function circleArea(r){
   return radius = 3.14*(r*r)
    
}
var r =prompt("What is the radius of your circle?'");

document.write("The area of the circle is "+ circleArea(r));  

console.log("Area =" +circleArea(r));

3. By Sharvil Khot

Made by Sharvil Khot. Source

21
Area of the circle is 1384.74
<!DOCTYPE html>
<html>
    <head>
        <title></title>
    </head>
    <body>
    <script type="text/Javascript">
    var r,area
    r=prompt("Enter the radius")
    area=3.14*r*r
    document.write("<h1>")
    document.write("Area of the circle is " +area);
    </script>
    </body>
    </html>

4. By Nishit Katole

Made by Nishit Katole. Circle area calculator with css styling. Source

JavaScript Circle Area Calculator by Nishit Katole
<!DOCTYPE html>
<html>
    <head>
        <title></title>
        <h1>Circle area calculator</h1>
    <style>
        body {
    background-color:hotpink;
    text-align:center;
    font-weight:800;
    font-family:cursive;
}

input{
    
   background-color:blue; 
   border:2px dashed yellow;
    border-radius:30%;
    height:30px;
    font-weight:900;
    color:cyan;
}


button{
    background-color:black;
    color:lime;
    font-weight:800;
    border-radius:13px;
    height:20px;
}
        </style>
    </head>
    <body>
        <hr color="blue">
        <br>
   <h2>Enter Number:</h2>   <br> <input type="text" id="radius">
        <br>
        <br />
        <button onclick="fun()">Get Area</button>
        <br><br />
        <h3 id="head"></h3>
        <script>
            function fun()
{
    var radius=document.getElementById("radius").value;
    var circlearea= 22/7 * (radius * radius);
    circlearea= circlearea.toFixed(2);
    document.getElementById("head").innerHTML=circlearea;
    
}
            </script>
    </body>
</html>

5. By Brain & Bones

Made by Brain & Bones. Source

22
Area of your circle is: 1520.5308443374597
<!DOCTYPE html>
<html>
	<head>
		<title>Page Title</title>
	<style>
        h1{
	font-size: 50px;
}
body{
	height: 450px;
	width: 350px;
}

        </style>
    </head>
	<body>
		<body bgcolor="red">
            <script>
                let r = prompt("Enter in the radius of the circle");
var x = (Math.PI) * r * r;
document.write( "<h1>Area of your circle is: " );
document.write(x)
                </script>
	</body>
</html>

6. By RedBlazerFlame

Made by RedBlazerFlame. Source

JavaScript Circle Area Calculator by RedBlazerFlame
<!DOCTYPE html>
<html>
	<head>
		<title>Page Title</title>
	</head>
	<body>
	<p id="header"><br/>Circle Helper</p>
	<div id="main">
	<input id="radius" placeholder="radius" oninput="p()">
	<button onclick="area()">Show Area</button>
	<button onclick="circum()">Show Circumference</button>
	<p id="answer"></p>
	</div>
	<script>
	//this was a program made by me 2 years ago, with my current knowledge, i have fixed and improved this old program

var pi=Math.PI;
var r=0;
function p(){
    r=radius.value;
}
function area(){
	answer.innerHTML=pi*r*r+" square units";
}
function circum(){
	answer.innerHTML=2*pi*r+" units";
}
addEventListener('resize',resize);
function resize(){
    main.style.width=window.innerWidth;
}
var red=255;
var green=0;
var blue=0;
var kf=0;
var rainbow=setInterval(changecolor,0.1)
function changecolor(){
    if(kf<255){
        red=red-1;
        green=green+1;
    }
    else if(kf>=255 && kf<510){
      green=green-1;
      blue=blue+1;
    }
    else if(kf>=510 && kf<765){
    blue=blue-1;
    red=red+1;
    }
    else{
        kf=0;
    }
    average=127.5*Math.sin(2*pi*kf/765)+127.5;
    main.style.background="rgb("+red+","+green+","+blue+")";
    main.style.border="10px groove rgb("+average+","+average+","+average+")";
    ++kf;
}
</script>
<style>
#main{
   background-color:rgb(255,0,0); 
   width:window.innerWidth;
   height:100px;
   border-radius:20px;
   border:10px groove gray;
   margin-top:50px;
}
#header{
  font-family:arial;  
  font-size:25px;
  font-weight:bolder;
  text-align:center;
  background:#AAAAAA;
  box-shadow:inset -100px -10px 10px #FFFFFF,inset 100px 10px 10px #FFFFFF;
  margin:0;
  width:100vw;
  height:100px;
}

</style>
	</body>
</html>

7. By TwoPTwo

Made by TwoPTwo. JavaScript Area of circle program using event drive. Source

23
Area of circle is 1662.5714285714284 units.
<html>
<body>
        
<form name="f1" onsubmit="f()">
Enter a value for radius :<input type="number" name="t1"><br><br>
<input type="submit">
</form>
       
<script language="javascript">
        
        function f()
        {
          var d=f1.t1.value;
          document.write("Area of circle is " +(22/7)*d*d+" units.");
        }
        
</script>
</body>
</html>

8. By Roel

Made by Roel. Source

24
area:1809.5573684677208
<!DOCTYPE html>
<html>
    <head>
        <title></title>
        <style>
            #knop {
    background-color:rgb(240,240,240);
    border:3px solid;
    width:80px;
    height:20px;
    margin-top:210px;
    margin-left:130px;
    border-color:rgb(200,200,200)
    rgb(120,120,120)
    rgb(120,120,120)
    rgb(200,200,200);
}
.tekst {
    text-decoration:none;
    font-family:"Arial Black";
    text-color:red;
}

            </style>
    </head>
    <body>
        <div align="center" id="knop"><b class="tekst"><a href="https://code.sololearn.com/WEj00YimiCZi/?ref=app">HELP</a></b></div>
    <script>
var r=prompt("Enter your circle's radius (diameter/2)");
var d=r*r;
var opp=d*Math.PI;
var o=r*Math.PI;
alert("your circle's area = "+opp+" m2/cm2/whatever");
alert("your circle's circumference = "+o+" m/cm/whatever");
document.write("area:"+opp);
document.write(" circumference:"+o);
        </script>
    </body>
</html>

9. By Gangineni Goutham Choudary

Made by Gangineni Goutham Choudary. Simple Circle Area finder. Source

25
1963.4954084936207
var rad=Number(prompt("Enter radius of the Circle."));
var pi=Math.PI;
var rsqr=rad*rad;
document.write(pi*rsqr)

10. By Nico

Made by Nico. Source

26
The area of a circle with radius 26 is 2123.7166338267
var radius = prompt("Enter radius", "");
    var answer = (radius*radius)*Math.PI;
alert("The area of a circle with radius "+ radius + " is " + answer);