How many square feet in a 1 foot diameter circle?

The area of a circle is PI times the radius of the circle squared.

The radius of a one foot diameter circle it 1/2 or .5 feet.

.5 squared is .25 PI is 3.1416

3.1416 times .25 = .79 square feet

So, there are about .8 square feet in a 1 foot diameter circle.