quote:When hanging down loosely, the average penis is about 3.75 inches long. During erection, its internal cylinders fill with so much blood that they become rigid, and the penis stretches to an average length of 6.25 inches. About 90% of all men have erect penises measuring between 5 and 7 inches in length. There is no relation, however, between penis size and female sexual satisfaction; a woman's vagina naturally adjusts during intercourse to the size of her partner's penis.
- An Invitation to Health, 8th edition, Diane Hale, p.251
