Analysis of information sources in references of the Wikipedia article "Layer cake" in English language version.
9" – 2 layer cake. Yield: 16 servings
You can also convert a sheet cake recipe into a layer cake....bake the sheet cake as directed and then make a squared-off layer cake. Cut the cooled sheet cake in half crosswise to yield two layers...
Keep in mind that the number of servings is subjective, dependent on the style of the cake, who is slicing it, and the size of the pieces guests request (wedding cake slices, for example, are smaller than standard sizes).