The Size Question
If you've been reading this column since the beginning, you should know that human genitals are widely varied and there's no one perfect form. But that doesn't stop us from constantly wondering how we measure up when compared to others. When surveyed, the majority of men admit they wish their penises were bigger and women worry about whether our vaginas are tight enough or too tight, not to mention the aesthetic question. Men especially seem preoccupied with the size issue. If I had a nickel for every time a guy had asked me if he was "the biggest" I'd ever had, I'd have...well, at least one nickel for every guy I've ever slept with. And the sad thing is, I don't really care that much about size -- it doesn't tend to correlate with my satisfaction from the act. There are size queens out there who'll turn down a guy for being too small, but there are just as many women who get scared off by a dick that looks too big to take comfortably. Everybody has a preference, but bigger isn't necessarily better.
The average human penis is about 3.5 +/- 1.0 inches (~8.85 cm) in length and 3.8 +/- 0.5 inches (~9.71 cm) in circumference when flaccid, and 5 +/- 1.1 inches (~12.89 cm) in length and 4.8 +/- 0.52 inches (~12.3 cm) in circumference when erect. The numbers for the flaccid state are roughly the same for both self-reporting and measurements taken by researchers, but self-reporting estimates the erect length at 5.8-6.5 inches, so there might be some exaggeration going on when men are asked to measure themselves. The question of course, is how much length and girth is needed to please your partner, and there the issue gets a little murky. Vaginas are meant to expand in both width and length when aroused, so they can accommodate a wide range of penis sizes comfortably. In one survey, 45 out of 50 women said that girth was more important than length when it came to their sexual enjoyment, though a specific ideal size wasn't given. (I'd say that my personal taste lies in this direction, but it's not the only, or even the most important, factor when it comes to sex.) Surveys on length preference are less conclusive. Some find that most women have no preference for any length while others show a definite partiality to longer dicks.
My guess is that such preferences are highly individual and based on the woman's own anatomy. Presumably, with the right moves, a smaller penis is just as capable of satisfying most women as a larger one, but there's likely to be some need for physical compatibility. The G-spot is generally assumed to be located between 1 and 3 inches deep on the front wall of the vagina, so even a very short member is capable of reaching it, and the highest density of nerves in the vagina is near the entrance, so length isn't necessary to provide a lot of stimulation. The cervix also has a lot of nerves, and some women enjoy having their cervix bumped, but others find it painful, making a long penis a bonus for some and a problem for others. Not to mention that for a lot of women what you do to the clitoris is more important than what's going on in the vagina. Vaginas vary dramatically in size as well and some penises may just fit better than others. If you happen to be small a larger penis can be physically uncomfortable while a smaller one may get the job done without pain. Conversely, a woman with a larger vagina may not get as much stimulation as she prefers from a smaller penis. (I didn't find any data on this, but I assume gay bottoms also have personal preferences based on anatomy rather than an arbitrary preference for big penises.)
The average vagina ranges from 2.75-5.75 inches (6.95-14.6 cm) in length and 0.8-1.4 inches (2.1-3.5 cm) in circumference at the entrance when not aroused, but has the ability to expand when aroused (or during childbirth, obviously). Not surprisingly, the size of a woman's vagina is roughly proportional to her overall size -- petite women tend to have small vaginas while taller women tend to have larger ones (I assume penis size also correlates with overall build -- that's certainly been my personal observation). Having given birth and age generally correlate with increases in size of the vagina, but unlike men and penis length, women have some control over such things, since the vagina is basically a muscle and can be exercised to increase tightness. However, being too "tight" is at least as common a worry among women as being too "loose." (I really hate using the terms "loose" and "tight" in reference to vaginas, by the way, since they're based on the presumption that one is better than the other.) While in theory the vagina should be able to stretch enough to fit a range of penis sizes, some women have trouble relaxing enough during sex, leading to discomfort and pain (lack of arousal beforehand can contribute to this problem -- it's not just lubrication but also the loosening of the vaginal muscles that makes penetration comfortable). In rare cases, the muscles involuntarily clench so tightly that penetration is impossible (a condition called vaginismus).
There's some evidence that while physiologically most women don't require a huge cock for sexual pleasure, some prefer one for psychological reasons. Our culture's "bigger is better" mentality may lead some women to choose to skip sex with less well-endowed men in favor of men who fit their stereotypical definition of masculine (i.e. big). Those women are idiots. That said, some penis sizes will work for some women and others won't, and the same can probably be said of vaginas and men. If a partner isn't satisfied with what you have, try thinking of it not as a personal inadequacy but a compatibility issue - like trying to fit the wrong puzzle pieces together. It's not that either piece has anything wrong with it; they just don't happen to work together.
Dr. Pisaster has a doctorate in biophysics, not actually anything sexy. She does however enjoy having sex, reading about sex, and talking about sex. Especially when she's had a little whiskey.