Is Bigger Really Better?

I have to confess, when I saw a global map of average penis size flying around twitter, I was like a eighth grade boy finding his first nudie magazine - I couldn't help but take a peek. After a brief heart attack (it's in cm, not inches), my inner scientist started asking silly questions. You know, the kind of things that would only occur to a scientist when looking at a map of penis size like, "is this just a stochastic distribution?" "is there any reason why this pattern would occur?" and of course, "does penis size even matter from an evolutionary perspective?!"

Turns out that inner scientist of mine is quite the nag. I couldn't get through the weekend without investigating her questions a little bit, just to shut her up.

There's no doubt that people seem to think size matters. Men certainly do. Culturally, penis length is intrinsically linked to a man's sexual prowess and masculinity. After all, it's entirely common to hear a man's penis referred to as his "manhood." Men are much more likely than women to report caring about their size. They also tend to sell themselves short compared to other men - most men who think they are small are actually average size1.

Women, on the other hand, seem to be more ambivalent. After all, less than 1/4 of women in one study reported caring about the length2. This might be partly due to the fact that women have a positively skewed view of penis length. One study, for example, found that only 6% of women thought their man's penis was below average, while 24% thought they had a well-endowed beau1. Statistically speaking, ladies, that's just not true. (But hey, what matters is that they're satisfied, right? Because the vast majority of those women - 84% - are.)

Of course, what people say and what they really feel aren't always synonymous. While many women say that's it's not 'the size of the boat' but instead 'the motion of the ocean' that counts, empirical studies have called them out on their bluff. For example, a study in China found that women found images of men more attractive if they were altered to have a 22%-33% increase in length3. Furthermore, the more partners a woman has had, the more likely she is to think length matters (and those with experience would know best, wouldn't they?)4.

But is bigger really better?

Well, that is the question, now isn't it? When I say "better", I'm really referring to one of two possibilities: 1) that size correlates strongly to pleasure experienced by the woman or 2) that increased size enhances reproductive success for the man. The two aren't entirely unrelated, as one might expect a highly talented man to have many willing partners. But in the latter, I'm more interested in a direct effect, as in length correlating to how much sperm is deposited, or the depth into the vagina somehow leading to higher chance of fertilization.

Screen shot 2011-03-27 at 6.46.00 AM.pngBut first things first: does how long your schlong is matter in bed? The short answer is yes, but bigger isn't always better. Think about it: at a certain point, you'd expect length would become... well, to put it bluntly, a big problem. After all, a woman's vagina is only so deep. Studies tend to agree. Women almost unanimously report being able to feel the difference between men, but only 5% felt length correlated with pleasure (girth, on the other hand...)5. Furthermore, while empirical studies have found modest enhancements of length are preferred, the largest extensions were seen as less favorable3.

There's good reason to think that penis size might matter from an evolutionary standpoint, too. After all, human males carry around a penis that is substantially larger than other primates6. There are several theories on why longer might be better. For example, it is thought that the deeper the placement of sperm, the more likely a woman is to get pregnant. There is also some postulating that a longer penis leads to increased frequency of orgasm for the woman during intercourse, which is also thought to lead to an increased likelihood of pregnancy (e.g. this, by Scicurious).

However, surprisingly scant evidence can be found which supports any theory of penis length and reproductive fitness. No study has correlated penis length with fertilization or even orgasm frequency. The only study I could find, in fact, looked at a completely different hypothesis. Gallup et al.7 attempted to determine if the human penis might function as both as a semen delivery and a semen removal device. Scicurious did a great breakdown if you're interested, but to quickly summarize, their theory was that if a man penetrated a woman soon after another had finished, his penis would "scoop out" the semen left by the woman's previous lover. They did find that the deeper the penetration, the more semen was displaced during simulated intercourse. However, they failed to take into account that their model penises were not representative of an uncircumcised man, and thus may not be as relevant to evolutionary history.

Really, there's very little evidence to suggest that size matters much at all. Certainly, men who are less than the global average reproduce effectively - the rapidly expanding populations in China and India are proof of that. So what does explain the pattern of penis size across the globe?

Well, you certainly can't rule out chance. When populations of a species are separated for a long enough amount of time, genetic changes that have nothing to do with selection accumulate - a principle which is known as genetic drift. The variation we see in penis size across the globe might simply reflect random shifts between ancestral populations.

Of course, it's also important to note that the penis lengths reported in the global chart aren't normalized in any way. Let's think of a different trait - weight, for example. If I said one person weighed more than another, the first thing you'd probably wonder is if they're the same height. Well, here's the same world graph, but this time looking at average male height:

It's not surprising that some of the shortest countries are short in many ways. Previous studies have found that penis size does correlate with overall height8,9. There are plenty of other environmental variables that could be in play, too. Diet, nutritional status, and many other factors affect growth of the human body in general, and could certainly affect growth 'down there'.

It's also important to note that the lengths weren't all measured in the same way - some were self-reported size, which scientists have found tends to be larger than the size measured clinically1. Nor are they from the same year - it's well established that average heights of people are shifting continually. Furthermore the weights of the men examined, whether they were from an urban or rural environment, and even the participants' age range vary between the studies. All of these variables are correlated with penis length. Without accounting for these factors, it's hard to compare the country averages in the first place.

All and all, while we might pass around such a map and giggle with our friends, the actual data involved aren't that informative scientifically. We simply can't determine if any pattern is occurring in penis length globally, and if it is, whether it is genetic drift or selection of some kind without a lot more information.


But feel free to giggle and pass it on anyway... I did!


1. Lever, J., Frederick, D., & Peplau, L. (2006). Does Size Matter? Men's and Women's Views on Penis Size Across the Lifespan. Psychology of Men & Masculinity, 7 (3), 129-143 DOI: 10.1037/1524-9220.7.3.129
2. Francken, A. (2002). What Importance Do Women Attribute to the Size of the Penis? European Urology, 42 (5), 426-431 DOI: 10.1016/S0302-2838(02)00396-2
3. Dixson, B., Dixson, A., Li, B., & Anderson, M. (2007). Studies of human physique and sexual attractiveness: Sexual preferences of men and women in China American Journal of Human Biology, 19 (1), 88-95 DOI: 10.1002/ajhb.20584
4. Å tulhofer, A. (2006). How (Un)Important Is Penis Size for Women with Heterosexual Experience? Archives of Sexual Behavior, 35 (1), 5-6 DOI: 10.1007/s10508-006-8989-7
5. Eisenman, R. (2001). Penis size: Survey of female perceptions of sexual satisfaction BMC Women's Health, 1 (1) DOI: 10.1186/1472-6874-1-1
6. Small, Meredith F. (1995). What's Love Got to Do With It? The Evolution of Human Mating. Anchor Books. ISBN 0385477023.
Gallup, G. (2003). The human penis as a semen displacement device Evolution and Human Behavior, 24 (4), 277-289 DOI: 10.1016/S1090-5138(03)00016-3
8. Edwards, R. (1998). The deï¬nitive penis size survey
results (6th ed.). Retrieved March 27, 2010, from
Ponchietti R, Mondaini N, Bonafè M, Di Loro F, Biscioni S, & Masieri L (2001). Penile length and circumference: a study on 3,300 young Italian males. European urology, 39 (2), 183-6 PMID: 11223678

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Do you think there's a correlation between lacking a penis and blogging about penises? I'm extremely wary of making this comment, as I don't want to turn this into a fierce gender discussion, but I'm honestly curious. I see more blogging about sex from the female bloggers that I read than the male bloggers I read, and I read way more male bloggers than female ones (a problem in itsself that I'm trying to fix).

The stereotype is that men think about sex more often than women, so why would women blog about it more? (perhaps it's just asample size issue)

I've read that the large amount of soy that Asians eat negatively influences penis size because of the plan-based estrogen soy contains.

Just reporting the mean size does not say much. Are these means significantly different (i.e statistically) from each other? You'd want to, at least, have the variances around the means. I assume the original paper must have said something about this. Until then, there's no story.

Hard to stop laughing. I want to suggest to guy wondering about women bloggers re sex. I think it has to do with a healthy curiosity and lack of paranoia, but I think you'd have to conduct a study to be sure.

Should have written "plant-based estrogen" not "plan-based estrogen."

Curious why no-one has ever done a study on dimensions of the vagina. Perhaps size matters only in relation to relative dimensions of both partners rather than the absolute dimensions of one.

"One study, for example, found that only 6% of women thought their man's penis was below average, while 24% thought they had a well-endowed beau1. Statistically speaking, ladies, that's just not true."

Perhaps men with small penises are less likely to be in a sexual relationship with a woman?

I would love to see one broken down by U.S. state. Mainly so I can make fun of friends from states that are dragging the average down.

@ Vaughan: Vaginas most likely differ in length (depth) but since they have the ability to stretch widely enough to allow the passage of a child they most likely 'auto adjust' to accommodate the girth of any given penis.

Chuck, I think that falls into the "be careful what you wish for" category.

Kevin, just because it is a stereotype does not mean it is factually accurate. They are a broad generalization of a group with similar characteristics (or just one defining characteristic). Though, I am sure there is a reason for such a disparity, assuming scientific proof could be gathered as opposed to anecdotal evidence. Perhaps it boils down to most straight men not wanting to stare at and study the wangs of other men (we have out own to play with, after all)? Hopefully that didn't make me sound anti-LGBT...

When I say "better", I'm really referring to one of two possibilities: 1) that size correlates strongly to pleasure experienced by the woman or 2) that increased size enhances reproductive success for the man.

This is surely too narrow a set to identify evolutionary pressure and other selective processes may well have been involved. You rightly point out the disparity between human penis size and that of other primates, notably our nearest relatives, from which it is resonable to suggest that the human penis is the result of either:

a morphological change which coincidentally produces increased penis length/mass â a result which is unchallenged by any overriding evolutionary cost (increased exposure to damage, disease etc.)
a specific evolutionary pressure for increased penis length/mass, which outpaces any competing evolutionary cost (increased exposure to damage, disease etc.)

Enhanced reproductive success, or mate selection (female choice) could certainly provide the relevant evolutionary pressures. Mechanical processes as you have noted, have previously been proposed, but these would equally apply to the other great apes, so some explantion is required for why humans need more specific semen placement or greater semen expelling capacity. In evolutionary terms female pleasure as a driving factor, is equally problematic given that nullipararic, the young homonin female will likely have limited experience of penetrative pleasure and therefore little reference to make a judgement about desirable penis size, and that post birth, that same female may have a different experience of penetrative pleasure, given the changes that expelling a large headed baby causes to the vagina.

An unanswered but significant question is whether penis girth (the often quoted basis to female penetrative pleasure) is tied to penis length, that is, does the physiology of the human penis allow increased girth without increased length. If female penetrative pleasure were the driving evolutionary factor one would expect a change in penis shape to be the result, not simply increased length, however this would not be achieveable if the morphology of the penis does not allow this.

Some of these problems are overcome if the human penis is considered not in mechanical terms â whether semen deposition/removal or in the delivery of penetrative pleasure â but in display and visual cue terms, particularly those of the erect penis as distinct from the simple mass of the unerect penis. The erect penis is effectively a set of blood filled tubes arranged around a central semen delivery tube, its performance, character and function are wholly different from those of the unerect state. In fully bipedal hominins the penis is more frequently exposed to damage, but it also is positioned more prominently for display, than is the case in non fully bipedal hominin relatives. Bipedalism would seem to be the point at which evolutionary pressure on homonin penis length would come into play.

If one were to take the bonobo as a behaviour model, where female mediated sexual interaction is the basis for group bonding, then males possessing a visually significant display of social/sexual availability and of vulnerability would be supported strongly within the group and benefit from both availability of breeding females and the security of male and female âfriendsâ confering survivability and a long breeding lifetime. The long penis as an advertisment of friendship may be far more sustainable in evolutinary terms than any Alpha male machismo.

I certainly enjoyed this article, and I love having bad science pointed out to me.

I would like to offer a bit of information I have though, from experience (not that anyone asked). I am quite a small person, and I definitely DO NOT prefer larger. When with larger partners I have been in pain more and have gotten many UTIs. With smaller partners I am satisfied,and pain- and infection-free. I also orgasm more frequently. So there.

It doesn't seem like it would be all that difficult to take penis size of different species and compare that to their birth rates. Taking out the fact that that rate is different among different species, if you could compare animals based on that number wouldn't it show how important penis size is? (I suspect not very.)

Not sure that made much sense, but I'm rusty on my statistics terminology and lacking in experimental procedure experience.

How does this affect emigrants? For instance, I see that if a man moves from Central or South America into the USA, he gets taller, but his penis shrinks, whereas men who migrate from the Indian subcontinent to the UK gain both height and length, as do those who move north from the US into Canada.

Is this the real reason for global migration?

Let it be clear to those who are concerned as to size is what you measure or measurable for others and those who read if not the text but the title of Shakespeare "Measure for Measure" does know Shakespeare with his titkle of the Play does allude us to the notion of equal perception in measurement.And May I suggest do we have equal perception even about equals?

"Vaginas most likely differ in length (depth) but since they have the ability to stretch widely enough to allow the passage of a child they most likely 'auto adjust' to accommodate the girth of any given penis." - Zusiqu

@Zusiqu, this is not entirely true. I've known several women, including myself who find coitus with larger sized men to be excruciatingly painful, and therefore not pleasurable at all. The vaginal canal may expand but that does not mean that it does so painlessly or pleasurably.
I've also found that men with smaller penises tend to be better lovers, but that may have more to do with the fact that they've realized that good sex involves a lot more than just intercourse, especially where female orgasm was concerned. Many women don't orgasm during intercourse (for whatever reason), and require clitoral stimulation in order to reach climax. This does not mean that males with larger penises are worse off, but that there is definitely some importance in the ratio of vagina to penis size, at least where pleasure is concerned. Evolution, on the other hand, may have a different opinion. ;)

Isn't there a hand-and-glove issue here? I mean as it relates to the correlation between girth and pleasure? A small vagina would seem to be just as "good" as a thick penis. Don't men say they prefer tight vaginas? I think so. Yet I have never seen these two issues discussed in common.

Bigger is not necessarily better, but there are certainly some things you can do with a bigger one, which wouldn't be possible with a small shaft.
But again, what's big and what's small? It's all in your mind!

Kevin @2

I see more blogging about sex from the female bloggers that I read than the male bloggers I read

I blame Scicurious mostly :)

I am amazed that there were 23 comments before any penis enlargement spam showed up.

By Militant Agnostic (not verified) on 16 Apr 2011 #permalink

Have you made any effort to verify that this is real data, and not someone on the internet making up numbers to be funny?

The link to takes me to

At the top it says "This website provide statistical information offered by trusted research centers and reports worldwide." The provide/provides slip-up does not look very authentic.

Their list of sources is a mix of real journals and sources like the magazine FHM. No attempt is made to correlate the pieces of data with the particular source.

When you look at data by country you get a hilarious and somewhat unprofessional image of a huge black penis. A great deal of effort seems to have gone into drawing dozens of penises so that the graphic varies from page to page. On each country's page is a columns is for "lenght". Another page has a column for "avarage" penis size.

They have a column for median age - um, why do we care? This certainly cannot be the median for people in the study, for an age is given even when no data is available for the country.

There's also the amusing fact that countries where penises were measured are an inch or so shorter than countries where the lengths are self-reported.

And where did this data come from in the first place? Are random people subjecting themselves to a penis examination at a high enough rate to get legitimate data? Are they asking people: "do you have a seven inch penis" and simply believing the answer?

Always make sure the data is real before finding an explanation for the data!

What about the male-to-male dominance factor? In male-dominated groups, the guy with the larger display might intimidate his fellow males and thus be more likely to have access to the females.

If this is the reason for the larger size, we'd tend to see larger sizes in areas where alpha males control access to females than in areas where females select mates. Because dick-waving is a lot more consistent (and stupid, but that doesn't matter) than whether a woman thinks size matters. But that tends to be a cultural artifact, and I kind of suspect not stabile over evolutionarily significant time frames.

If course bigger/longer is better. If one simply considers the mechanics of coitus it becomes clear that it is much easier to maintain contact between genitalia through all the phases of the intercourse. Certainly in the pre-orgasm and orgasm stages more exaggerated movements make it more difficult to maintain contact using a shorter penis. It must be thoroughly frustrating to women to have to deal with the re-entry issues when they were already ever so close to the "promised land." To boot, the additional psychological input certainly enhances the physical neurological response.

The whole "size is not important movement" is nothing more than a cash cow for therapists, psychologists, etc... who otherwise have no qualifications to make a living. But for a large fee they will tell half-cocked men that everything is alright.

By Pensive Introvert (not verified) on 15 May 2011 #permalink

Hi! dis article is very helpful. eventhough i am a virgin bt i read so stuffs. i think size matters alot. small penis size wil b better. it cause less pain. d average penis
size(5-7)inches tends 2 be larger than d average vagina depth(4-6) inches. so dis tels u a small penis wil never exceed d average women's range. moreover, one of d most plearable orgasm
is achieved though low level penatration not deep which makes small penis stands a better chance than larger ones.

I think bigger is always better.. Thats what I feel anyways... there are a lot of interesting discussions going on about this subject I have to say..

No woman will tell you the truth about her preference size especially if a guy asks her. let me ask you. Will a woman tell you any compliment about your tool if it is small or average? But if it is bigger,she will. Ask any woman this old bullshit question" does size matter?" every woman will answer " size does not matter , only the way you use it does". And if you know you're blessed down with big dick , show her and you will see the hidden truth.

By Bigbetter (not verified) on 26 Feb 2012 #permalink