Description: The area of a circle is pi times the radius squared (A = π r²). Learn how to use this formula to find the area of a circle when given the diameter. Created by Sal Khan and Monterey Institute for Technology and Education. - [Teacher] A candy machine creates small chocolate wafers in the shape of circular discs. And so when we think about area, we know that the area of a circle, the area of a circle is equal to pi times the radius of the circle squared. So the area is going to be equal to pi times eight millimeters squared, which would be 64, 64 square, 64 square millimeters.*Teacher Advisor is 100% free.