To find this answer you need to find the area of the whole cake and divide it by 8. To find area of a circle, you need the formula (pi)*r^2. The radius is the diameter divided by two. Your final formula would be (pi)*8^2. This is approx. 201.06 in^2. Divide this number by 8, and you have your answer. I got 25.13 in^2.