What if your penis is small why is it?

The average penis size for a 14 year old is about 4 inches. HOWEVER, the age at which puberty typically begins is anywhere between 10 and 15 years old. So the penis size for a 14 year old can range from prepubertal (About 2 inches) to Adult (6+ inches). At 14 years old it would be normal to have a penis anywhere in that range.