Circle Math – A Well Rounded Education

There are a lot of clichés to choose from for a blog about circle math.  What goes around comes around, a new spin on math, or it’s easy as PI.  Regardless of the corny ways to describe the subject, there is no denying the importance of knowing the basic math associated with circles.  We rely on circles heavily in our daily lives.  Imagine a world without wheels, circular planets, and (most important to me) round food like pizza and hamburgers.  There are so many aspects in our lives that we rely on circles and spheres that is why it is important to know the basic math associated with them.

The most important mathematical ingredient to understand on this subject is Pi.  This is a constant number used when calculating different aspects of circles.  The actual number of Pi is approximately 3.141592654….it actually has a never ending amount of numbers after the decimal.  In most math classes it suffices to use 3.14 or 3.1416 for more specific answers.

In addition to PI, there is the radius and diameter.  The radius is the amount of distance from the center of the circle to the outside of the circle.  The diameter is the distance of a line that bisects the circle from one side to the other and crosses through the center.  The diameter of a circle is always twice the distance as the radius.

Circle Radius and Diameter
There are no corners, or even sides to this shape.  It is a continuous curve around a common point.  The outside of a circle is called a circumference.  It’s similar to the perimeter of other shapes, but since there isn’t a side, just a constant curve, it’s called a circumference.  To calculate the circumference of a circle you need to know the radius length and Pi.  The equation is:  2 x Pi x R where R is the radius.  Sometimes you’ll also see this equation used with the diameter.  Because the diameter is twice the distance as the radius, the equation would be: Pi x D where D is the Diameter.

The area of a circle is also important.  ( I want to know how much pizza I’m eating )  To calculate the area of a circle, you can use Pi and the radius again.  The equation to find the area is: Pi x R².  If you take the square of the radius and multiply that by Pi you will have the area.

Since the sphere is the 3-D version of the circle, the math to calculate the surface area and volume only slightly more complex.  You can use the following equation to calculate the surface area of a sphere:  4 x Pi x R².  To calculate the volume of a sphere, use the equation:   4/3 x Pi x R³.

Now you have the basic math for circles and spheres.  What you can do with this mathematical power is nearly limitless.  You can calculate the volume of the Earth, you can calculate the surface area of a baseball, or like me, you can find out the area of a pizza.


CalcuNATION is a website featuring online calculators and educational resources for mathematics.  Other Mathematical Blogs ( CalcuNATION on EduBlogs and CalcuNATION on Blogger)

Leave a Reply