The area of a circle is PiR^2, or Pi x r x r.
Since we have the circumference formula, PiD or 2PiR, or 2 x pi x r/pi x d, we can find the area easier.
First, divide 16 by 2, as 16 is the diameter, and the radius is half of the diameter.
8 is our radius, so now we must use our formula.
Pi x R x R.
8 x 8 x 3.14 (standard pi).
64 x 3.14
Your area is 200.96 units^2.
If you are being exact, 201.96 units^2.
I hope this helps!