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Radius of a Circle Calculator

Radius of a Circle Calculator


Circumference (c)


Area (A)



Table of Content

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Our radius of a circle calculator helps you to find the distance from the centre of a circle to any point to its edge.

How Does This Radius of a Circle Calculator Work?

Truly uttering, our calculator is pretty easy to use if you stick to the following usage guide!


  • From the first drop-down list, select the parameter with which you wish to carry the calculations
  • After that, enter its value along with the unit selected from the next list
  • At last, hit the “Calculate” button


  • Radius, area, diameter, and circumference of the circle

What is the Radius of a Circle?

You all may be familiar with a circle, a well-known and widely used geometrical figure.

“The distance from the center of a circle to any of its points on the circumference is known as the radius”


Radius of a circle

How to Find the Radius of a Circle?

In geometry, a circle is defined by many related entities. And if you are willing to find its radius given different parameters, then these include:

Radius of a Circle Formula:

From Diameter:

Radius from Diameter

As we know that:


From Area:

Radius from Area
You know that:


From Circumference:

Radius from Circumference
As you know that:


From Area and Central Angle of a Sector:

Radius from central angle and area
You know that:



Let us resolve an example that may help you in finding radius of a circle:


What’s the radius of a circle having area as \(78m^{2}\)?








From the source of Wikipedia: Radius, Formula, Use in coordinate systems

From the source of Khan Academy: Radius, diameter, circumference & π, Labeling, Area of parts of circles

From the source of Lumen Learning: Circles, Equation of a Circle in Standard Form, General form of a circle