# How to Calculate the Arc Length of a Sector in JavaScript

09/30/2021

Contents

In this article, you will learn how to calculate the arc length of a sector in JavaScript.

## Calculating the arc length of a sector in JavaScript

The arc length of a sector is the length of the portion of the circumference of a circle that corresponds to the central angle of the sector. In JavaScript, we can use the following formula to calculate the arc length of a sector:

``Arc Length = (central angle / 360) * 2 * π * r``

where central angle is the angle subtended by the sector at the center of the circle (in degrees), r is the radius of the circle, and π is the mathematical constant pi, which is approximately equal to 3.14159.

### Examples

#### Calculating the arc length of a sector with a central angle of 60 degrees and a radius of 5 units

``````const centralAngle = 60; // in degrees
const radius = 5; // in units
const arcLength = (centralAngle / 360) * 2 * Math.PI * radius;
console.log(arcLength); // 5.235987755982989
``````

In this example, the central angle is 60 degrees, the radius is 5 units, and the output is the arc length of the sector, which is approximately 5.236 units.

#### Calculating the arc length of a sector with a central angle of 120 degrees and a radius of 3.5 units

``````const centralAngle = 120; // in degrees
const radius = 3.5; // in units
const arcLength = (centralAngle / 360) * 2 * Math.PI * radius;
console.log(arcLength); // 7.266478599682293
``````

In this example, the central angle is 120 degrees, the radius is 3.5 units, and the output is the arc length of the sector, which is approximately 7.266 units.

#### Calculating the arc length of a semicircle with a radius of 10 units

``````const centralAngle = 180; // in degrees (since it's a semicircle)
const radius = 10; // in units
const arcLength = (centralAngle / 360) * 2 * Math.PI * radius;
console.log(arcLength); // 31.41592653589793
``````

In this example, the central angle is 180 degrees (since it’s a semicircle), the radius is 10 units, and the output is the arc length of the semicircle, which is approximately 31.416 units.

Note: If you have the length of the arc and you want to calculate the central angle, you can rearrange the formula as follows:

``Central Angle (in degrees) = (Arc Length / (2 * π * r)) * 360``