Circle Area Definition The Circle Area Calculator will instantly calculate the area of a circle if you simply enter in the circle’s radius. The radius of a circle is the distance from the middle of the circle to its outer edge in a straight line. The radius is equal to one half of a circle’s diameter (the diameter of a circle is the distance from one edge of a circle to the opposite edge in a straight line). This means that if you know either the diameter of a circle or the radius of a circle then you can just divide the diameter in half to get the radius or multiply the radius times two to get the diameter. Enter in the radius of the circle above to calculate the area of the circle.

How to Calculate Circle Area Let's be honest - sometimes the best circle area calculator is the one that is easy to use and doesn't require us to even know what the circle area formula is in the first place! But if you want to know the exact formula for calculating circle area then please check out the "Formula" box above.