Replying to 8th Grade math is kicking my ass.

someone help me with this embarassing problem.
i pitched for a blunt sesh about an hour ago and came home to do my english project.  im making a pyramid out of foam posterboard cutouts.  base is a 16x16in square.  i want the triangles to be equilateral with legs of 16in.  What will the height of my triangles be.  My blazed ass is all twisted up in pythagarus and square roots.  did the equation about six times and each time i came up with 17.8in.  i know thats not right its impossible.  help me out ns.