How to Calculate Round Area to Square Feet

By Anne Mullenniex; Updated April 24, 2017
A circle's circumference is the measurement of the total distance around the circle. The circumference divided by its diameter is the number represented by pi.

A square foot is a unit of measurement describing the area covered by a square. This is a two dimensional measurement and is calculated by multiplying length times width. When you look at a circle, you might imagine a square with the corners snipped off and rounded and wonder how to calculate this area without the missing corners. You’ll need the number represented by pi (~3.14) and a simple equation.

Find the radius of the circle. This is the measurement from the center of a circle to any point on its perimeter. It is also half the diameter, which is the total distance across a circle.

Multiply the radius times itself (this is called “squaring” the radius).

Multiply the resulting number times pi. For example, if you have a circle with the radius of 2 feet, then the equation would be A = pi x r x r = 3.141592 x 2 feet x 2 feet = 3.141592 x 4 square feet = 12.57 square feet.

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About the Author

Anne Mullenniex has been writing for eHow since 2009. She has owned and operated computer, construction, and insurance businesses. She has a bachelor's and a master's degree in biology and has taught at a community college. She is now working as an artist/artisan in multiple media.