Lining a baking pan with two pieces of aluminum foil makes it super easy to get baked brownies, cakes, and even granola bars out of the pan. The pieces of foil should be the same width as the pan and long enough to hang over the sides.
For an 8-inch square pan, both sheets of foil should measure 8 inches across and roughly 13 inches long.
For a 13-by-9-inch pan, one sheet should measure 13 inches wide and the other 9 inches wide. Both sheets should be about 18 inches long.