How to Find Radius From Circumference

The circumference and radius of a circle are contingent upon one another. The radius is the distance from the circle's center to any point on the circumference, and the circumference is the result of moving the radius around a full 360 degrees, which is the whole of the circle. The circumference is a product of the radius and the mathematical constant π or pi, which is a nonrepeating and nonterminating number that begins 3.14. The radius of a circle can be found from its circumference with the help of π.

Things You'll Need

• Calculator

Instructions

1. Find the measurement of the circumference. For this example, the circumference is 60 cm.

2. Divide the circumference in half. For this example, half of 60 is 30.

3. Divide the half of the circumference by π. For this example, 30 divided by π equals 9.55. The radius is 9.55 cm.

References

• Math Goodies: Circumference
• Math OpenRef: Radius of a Circle Definition
• Cool Math: The Geometry of Circles

Resources

• Calculator Soup: Circle Calculator