You are not the first woman to tell your boyfriend that he has a small penis. This question is common among men. It doesn’t matter if it’s true, men often know their size. Whether they are bigger, thicker or skinnier than the average, men are not fooled by it. It is incredibly demeaning to tell a man that he’s “enormous!” when he’s wearing an undersize piece of clothing. He will likely think you are sarcastic or insulting.