# How to set the radius of a Circle using FabricJS?

FabricJSJavascriptHTML5 Canvas

In this tutorial, we are going to learn how to set the radius of a Circle using FabricJS. We can specify the position, colour, opacity and dimension of a circle object in the canvas, but first we will have to specify a radius for our circle to show up. This can be done by using the radius property.

## Syntax

new fabric.Circle({ radius : Number }: Object)

## Parameters

• options (optional) − This parameter is an Object which provides additional customizations to our circle. Using this parameter, properties such as colour, cursor, stroke width and a lot of other properties can be changed related to the object of which radius is a property.

## Options Keys

• radius − This property which accepts a Number value. The value that is assigned, determines the radius of the circle.

## Example 1

Passing radius property as key

Let's see an example to set the radius of a circle in FabricJS. In this example, we have assigned the radius property a value of 50 which thus creates a circle with a 50px wide radius. It is possible to add decimal values as well.

<!DOCTYPE html>
<html>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>

<body>
<h2>Setting the radius of a circle using FabricJS</h2>
<p>Here we have set the <b>radius</b> at 50px. </p>
<canvas id="canvas"></canvas>

<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
var circle = new fabric.Circle({
left: 115,
top: 50,
fill: "#85bb65"
});
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
</script>
</body>
</html>

## Example 2

Passing the value as an expression instead of a single numerical value

Instead of passing a single numerical value, it is possible to assign an expression to the radius property as well. In this example, we have used the expression: [(30 * 3) + 10] which evaluates to 100 and hence the circle will have a radius of 100px.

<!DOCTYPE html>
<html>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>

<body>
<h2>Setting the radius of a circle using FabricJS</h2>
<p>Here we have set the radius at 100px, but instead of passing a single numerical value, we have used an expression [(30*3)+10].</p>
<canvas id="canvas"></canvas>

<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
var circle = new fabric.Circle({
left: 115,
top: 50,
radius: (30 * 3) + 10,
fill: "#ffa500"
});
</html>