It's easy to refer to 12 eggs as a 'dozen'. It's short and quick. It gets the point across easily with no confusion. Am I missing the obvious counterpart for 18 eggs? "1 1/2 dozen"? "Dozen-and-a-half"? "18-count"? I want my egg adverts to be clean and simple - and I know I'm over-thinking this, but I can't find a phrase that works.