If the circle is 5 feet around the circumference then there are 5 linear feet in the circumference. If you are asking what is the circumference of a circle with a 5 foot diameter then the answer is Pi x d
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.