There is no correlation between a person’s skeletal dimensions and their soft tissue dimensions. Example, your nose and ear sizes have little to do with your skull dimensions.
There are some proportions that do occur, Nose is the pretty much same length as the ears, the eyes are an eye width apart are 2 that are quite true (artists use this when drawing a face), when a person doesn’t fit those we tend to perceive them as odd looking.
The only hand/penis one I have heard that is a very rough guide is if you bend your middle finger down your palm and get it as close to your wrist as possible. Mark the spot the end of your middle finger reaches, open your hand and from the top of your middle finger to the marked spot is supposed to be your erect penis length.
Of course this would mean that a person with a micro penis either can’t close their hand or has the world’s smallest fingers, this is very much a rough guide for the average person.