Hiya carolyn!!! The sizes of the sites vary greatly from one to the next....to be honest, I dont think anyone here has exact measurements of any of them. Its fairly common knowledge that the 2000 loop has larger sites than the 1500 loop. Those are the only Tent/pop-up loops on the campgrounds. They have larger sand pads than the rest of the loops that are set up for Rvs. If you have a larger tent, and plan to have a screen house of some sort as well....2000 may be what your looking for, but 1500 is fine for an avg tent and a screen house.
Welcome to the dis camping boards. Hang out here for a while....theres plenty of information on Ft Wilderness that you dont even realize will come in handy...plus, the folks here are a trip. They get ya to laughing....or blushing...one of the two is guaranteed!!!