The size of the human penis is something that concerns all men. It is often seen as being a manifestation of one's manhood, and as such most men are interested in knowing how their own size compares to others. The average penis length is usually reported to be about 14 cm, or about 5.5 inches.
However, it is likely that this value is an underestimate. Since having a large penis size is so important, it is beneficial to both small and large men to deflate the average size. For small men, this helps one to feel more "normal", or to ease the internalized humiliation one can feel at being less than other men. For average or larger men, reducing the reported average has the benefit of making one feel more confident about one's size.