How to Find the Area & Radius of a Circle From the Circumference

The circumference of a circle can tell you much about it; not only can it tell you the size of the circle's perimeter, but also the size of the circle's other dimensions. The area of the circle is all of the space encompassed by the circumference, and the radius is the distance from the center of the circle to any point on its circumference. Finding a circle's area and radius through its circumference helps with understanding the circle's interrelated properties.

Things You'll Need

• Calculator

Instructions

1. Divide the circumference by π. For example, a circumference of 100 divided by π equals 31.83.

2. Divide that number in half to calculate the radius. For this example, 31.83 divided in half equals 15.915.

3. Square the radius and multiply it by π to calculate the area. For this example, 15.915 squared equals 253.287, and then multiplied by π equals 795.725.

References

• Math Goodies: Circumference
• Math Warehouse: Area of a Circle
• Math OpenRef: Radius of a Circle Definition

Resources

• Calculator Soup: Circle Calculator