5 Jul The ratio between the length of the index finger and the ring finger of men's hands is associated with penis length, a study shows. 4 Mar However, there is another relationship between hands and putative penis size, which relates to the length of the fingers — specifically, the index and ring fingers. A study published in the Asian Journal of Andrology used the same “gentle stretching” technique on a group of men, this time. 13 Sep While many men are insecure about the size of their penis, many women can to go great lengths (no pun intended) to learn how to find out his penis size. But thanks to one study, we now know that the ratio between the index and ring finger correlates to the size of a man's penis. So the next time you're.