How to Find the Area of a Circle In Geometry

Circles are found in many types of art forms.

A circle is defined as the set of all points in a plane equidistant from a single point. Finding the area of a circle will require a slightly more complex calculation than is the case with other two-dimensional figures, such as a square, rectangle or triangle. Students in prealgebra should be able to perform this calculation by memorizing a standard formula.

Things You'll Need

• Calculator

Instructions

1. Learn the formula for the area of a circle: A = (pi)(r)^2. Here the radius, r, is defined as the distance from the circle's center to any point on the circle's boundary. Pi is a mathematical constant, approximated at 3.14. Pi represents the ratio of a circle's circumference, or perimeter, to its diameter, which is defined as the twice the radius.

2. Select a circle to work with. For example, suppose your circle has a radius of 5 inches. First, square the radius. You would calculate 5^2 to get 25.

3. Multiply your response from Step 2 by 3.14. In the example, you would calculate 25 x 3.14 to get 78.5 square inches.

References

• Math Is Fun: Circle