Well, you don’t have to wait for him to drop his pants, only to be disappointed. Instead, just look at his hands.
If you really want to know how to how big his penis is without stripping him naked, the most accurate thing is the size and shape of his hands. Exposure to prenatal hormones may be to blame for this strange correlation.
According to Korean researchers from Gachon University, it turns out that when in the womb, the amount of prenatal testosterone that men are exposed to directly control both the hormone production in hands and penises. Therefore, higher doses of testosterone that lead to bigger hands can lead to other things being big too.
Besides the size of his hands, the way his fingers are shaped could give you an indication of what to expect. If his fingers are short and thick, chances are so is his penis. If they’re long but not very thick, then it suggests that he’s got length but not a lot of breadth.
And also it turns out that guys with shorter index finger than ring finger tend to have bigger penises than guys with the opposite digit scenario. “It all has to do with the gap in length between a man's ring finger and index finger. The shorter index finger than ring finger you have, the longer stretched penile length you have,” says Korean researchers from Gachon University.