The surface area will be 4 times the original size. Here is why: You are doubling each dimension, and area is a 2 dimensional measurement. Because of this whatever you are doing to the length of the side will happen 2 times. In this case it would be x2 x2 which equals 4. You can provide evident by using a cube. The surface area of a cube with side lengths of 1 would be 1 x 6=6 square inches. If you double the side length, it would be 4 x 6= 24 square inches.