A traditional serving size is one that we are all familiar with. A wedge shape slice where the cake is cut like a pie or pizza. This is also the more generous serving size. Wedges can be cut accordingly to allow for a generous large wedge & serve fewer guests or a more sensible wedge allowing your cake to serve a larger head count. The sensible portion is approximately a 2" by 2" square.
An event serving size is one that will allow your cake to go further. A typical event portion is a 1" by 2" square of cake. This serving is also sometimes referred to as a wedding cake serving.
This is a very difficult question to answer because everyone has a different idea about what size is a good portion to serve & receive. Some would be happy with a token gesture others (like me) would opt for a substantial chunk! Obviously there comes a point at which you have to make a decision, hence I have attached a cutting guide to assist you.
I want to ensure that you are truly delighted with your cake and therefore would prefer that you chose the size that best suits your appetite....