Almost all men have a normal size penis – although many young men are concerned that their penis is too short or too small. Sometimes they believe this because they have compared themselves with friends or classmates in a common shower or locker room, or maybe someone teased them or made a hurtful comment. Or they might have seen pornographic pictures or movies and compared themselves with the porno “stars” (many of whom have unusually large genitalia).
The penis reaches adult size over a number of years during puberty (the years during adolescence when boys and girls grow and change to become adult men and women). A boy who matures more slowly than his friends will not get an adult-size penis until late in adolescence – and this may cause anxiety or make him feel as though he has an abnormally small penis.
It is also worth noting that a man’s penis may change size considerably depending on time of day, temperature, and factors other than sexual stimulation or excitement. During sexual stimulation or excitement, the penis becomes engorged with blood and stands erect – but there is a wide variation in normal size and shape and angle for an erect penis also. In some men, the erect penis is almost the same size as the flaccid (soft or non-erect) penis, while in other men the erect penis is much longer and wider than the flaccid penis. You cannot tell by looking at a man’s flaccid penis what size it will be when erect.
As a general rule, the size of the penis does not determine a sexual partner’s satisfaction with a sexual experience. That usually depends much more on the relationship between the two people and on both partners trying to make each sexual experience mutually pleasurable and satisfying for both of them.
Because many young men are concerned about the size of their penis and would like it larger, there are many unethical people or businesses that offer lotions or pills or other types of non-medical treatment to enlarge or lengthen the penis. None of these methods have been fully tested in clinical trials and approved for medical use – and none of them are recommended by reputable physicians. They are taking advantage of a man’s concerns about his penis size (despite the fact that most men have a normal size penis) and seeking to get his money for treatments that are worthless at best. Some can be dangerous or may even damage the penis. None of these methods or products can be recommended or should be used.
Finally, there are a few uncommon medical conditions of the penis that a man should talk about with his doctor (especially a urologist). The first is an extremely small penis, a condition called micropenis in which the penis does not develop to a normal size. Occasionally a boy will also have a penis that does not develop normally even before birth; usually these conditions are recognized shortly after the baby boy is born and given the necessary medical attention. Another medical condition occurring most commonly in middle-aged men is Peyronie’s Disease. In this problem the penis develops scar tissue that may cause it to be smaller or curve abnormally – but this is not a cause of concern about a small or short penis in young men.
Wikipedia article on human penis size
Study: Men May Overestimate Normal Penis Size
WebMD: Penis Enlargement, Does it Work?