JavaScript program to find area of a circle

We will be using the below formula to find the area of a circle −

pi * r^2

In the program, we will prompt the user to input the radius of the circle. Then, we will use the formula to calculate the area and print it on the screen.


  • Get the radius of the circle from the user as an input.

  • Calculate the area using the formula: area = π * radius^2

  • Store the value of π, it can be calculated using Math.PI in JavaScript.

  • Multiply the value of π with the square of the radius to get the area.

  • Round off the result to required decimal places, if necessary, using the toFixed() method.

  • Return or print the calculated area.


Here is an example of a JavaScript program that calculates the area of a circle

const radius = 10;
const pi = Math.PI;
const areaOfCircle = (radius, pi) => {
   return pi * radius * radius;
console.log("The area of the circle is: " + areaOfCircle(radius, pi));


  • First, we declare two constants: radius and pi. The radius constant is assigned the value 10, and pi is assigned the value of Math.PI which is a built-in constant in JavaScript that represents the value of pi (3.14159...).

  • Next, we define a function named areaOfCircle that takes two parameters radius and pi.

  • Inside the function, we use the formula for the area of a circle, which is pi * radius * radius, and return the result.

  • Finally, we use console.log() to display the result of calling areaOfCircle with radius and pi as arguments. The result is a string that says "The area of the circle is: [area]".This program calculates the area of a circle with a radius of 10 and outputs the result to the console.