the sizes are either even or odd numbered. i usually use the even sizes. i have cake pans 4”, 6”, 8”, 10’’, 12”, 14”, 16” and 18”. the square pans give you added servings because they are full size. round and hexagon pans give you a little bit less servings. think about it this way: round, oval, rectangle and hexagon shapes are actually square shape trimmed on the sides. here are my own recommendations for number of servings per pan. these are generous slices and not considering single or double layers. the double layered cake will just be extra cake for your guests. 4” cakes will serve 6-8 people, 6” 