Video:How to Calculate Circumference

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Transcript:How to Calculate Circumference

Hello. Jesse here with About.com. Today I’m going to show you how to calculate the circumference of a circle.

Use a Formula to Calculate the Circumference of a Circle

The circumference of a circle is the distance around the outside of the circle. To calculate the circumference of a circle, you will need to use the formula C equals Pi times D. The C in this formula stands for Circumference – the value we’re trying to find. Pi is a special number in math, often represented by a Greek symbol or the value 3.14. The D in the formula stands for Diameter, which is the distance from one side of the circle to the other passing through the circle’s center. So, in this formula, to figure out the circumference of a circle, you will need to know what the diameter of the circle is and then multiply that by Pi.

The Radius of the Circle Can Determine the Circumference

There is another formula you can use to calculate the circumference of a circle. This is 2 times Pi times R. The R stands for the Radius of the circle. The radius of the circle is the distance from the center of the circle to the outside edge of the circle. Therefore the radius is half the size of the diameter and the diameter is twice the size of the radius.

Examples of Circumference Calculations

Here are some examples to show you how to calculate circumference. In this example we have a circle whose diameter has a value of 6. To calculate the circumference of the circle we have to multiply the value of Pi (3.14) times the value of the diameter, in this case, 6. Therefore the circumference of this circle is 18.84. Here is another example. This time we are given the radius, not the diameter. The radius has a value of 4. To calculate the circumference of the circle we have to multiply 2 times the value of Pi times the value of the radius, 4. Therefore the circumference of this circle is 25.12. Now you know how to calculate the circumference of a circle using either the radius or the diameter.

Thanks for watching. For more math instruction you can visit us on the web at math.about.com.