The Area and Circumference of Circles

  • John Adams Middle School Math Department Illustration of the circumference of a circle

    Area = Pi r2
    Circumference = Pi d

    What is a circle?

    A circle is a set of points equidistant from a center point. The distance from the center point to any point on the circle is the radius. The diameter of the circle is a chord that goes through the center. Its length is twice the length of the radius. The distance around a circle is the circumference.

    If you divide any circle's circumference by its diameter, you get Pi.
    Pi is approximately 3.14 or 22/7.