How to Calculate Circumference of Circles

The circumference of a circle is simply the distance around the circle. You can easily calculate the circumference of a circle if you know the radius. Learn how.

Difficulty: Easy

Instructions

1. 

   The formula used to calculate the circumference of any circle is:
   Circumference = 2 x Pi x Radius, where Pi is 3.14

2. Let's say you need to figure the circumference of a circle whose radius is 12 inches. Simply plug the number 12 into the equation for Radius. Again, Pi is 3.14. Your equation should now look like this.
   Circumference = 2 x 3.14 x 12
   Therefore, the circumference of a circle with a diameter of 12 would equal 75.36.

3. Another way to calculate the circumference of a circle is to multiply the diameter times Pi. If you are not given the diameter, simply multiply the radius by 2, since the diameter is two times the radius. Using the same example, let's calculate the circumference using the diameter.
   
   We know that the radius is 12. Since the diameter of a circle is two times the radius, our diameter would be 2 x 12, or 24.
   
   So, Circumference = Pi x Diameter = 3.14 x 24 = 75.36.
   
   As you see, we came to the same answer both ways.

Resources

• How to Calculate Area of a Triangle
• How to Calculate Area of a Circle
• How to Calculate Area of a Rectangle
• How to Calculate Area of a Trapezoid

[HowDragon]

on 3/15/2009 Good advice on calculating the circumference of a circle. Thanks! 5*!

[sonni57]

on 3/15/2009 Good info on how to calculate the circumference of a circle and well done.