NOTE: This page is pending a review and rewrite.
Penis size matters, but how does it matter? What sizes do people prefer, how much importance does it have, and how much do preferences vary across individuals?
Heterosexual Women's Penis Size Preferences
『Do all women prefer big dicks?』
No. Many women have no appreciable size preference, and the preferred sizes among women that do have notable size preferences are quite variable. there are some who prefer short, thin, average, long, thick, and any combination of lengths and girths therein. However, the average of these preferences is a little bit above the average male erect length and girth.
『So someone with a penis size that isn't at the most preferred region is at an overall disadvantage to someone who is?』
Sure, but the degree of disadvantage is usually so little that it would hardly matter for the vast majority of men.
In studies that specifically ask women to rate how male attractiveness is affected by different flaccid lengths, while they demonstrate an overall visual preference for above average lengths, the effects are usually less than those of other body-type attributes (these studies also suggest significant variation between different geographic populations of women, probably due to differences in cultural perceptions of penis size). In the following study data, the flaccid lengths relative to the model height would have the shortest at about 3 inches and longest at about 5.7 inches if one assumes the model has the average male height of about 5'9 - 5'10". Personally, I find such flaccid size data a bit incomplete since I'd expect women to associate larger displayed flaccid sizes with increased male arousal during partial erection, which could bias the results in favor of larger than typical flaccid sizes being more attractive in such simple visual comparisons.
Most women report that penis size matters very little: technique, erectile functionality, being able to last long enough, foreplay/oral, sexual interests, selflessness, etc. are all usually more important to them than the size of a man's penis. In relation to the importance of other physical properties, most women tend to find facial attractiveness, height, and fitness all more important for sexual attractiveness. To put it into perspective, the average woman reports slightly less importance for a partner's penis size than she does for whether or not a partner enjoys cooking or whether he has good taste in clothes, whereas penis size was on average only more important than trivial aspects like a partner's eye-color. Though when not looking at averages, preferences vary greatly so there are plenty of women who place a lot more or a lot less importance on penis size.
Data Source: Prause et al. 2015 Supplemental Data
『If it usually doesn't matter much then why do I always hear that women want big dicks?』
Popular western culture, media, and porn industries have been pushing the "bigger is better" notion for so long that big dicks have become normalized almost to the complete exclusion of anything else. To the point that I'd be surprised if it didn't cause many women to internalize that they should prefer larger than they actually prefer. But nonetheless, when you actually assess women's preferences it's clear that the popular notion is untrue, because the average of all their different preferences is consistently shown to be only a bit above the average penis size.
Johnston et al. 2014: Ask women what size they prefer.
Average Ideal Erect Length: 6.09" (0.79" above what they reported for the male average)
『Women self-reporting sizes? We can't expect people to give reliable distance estimates.』
Alright, then let's remove that problem.
Prause et al. 2015 - 3D Model Study: Have women choose their single most ideal size from among 3D-printed penis models of many different sizes.
Data Source: Prause et al. 2015 Supplemental Data
When averaged, all these women's penis size preferences yield:
Ideal Erect Length: 6.39" (0.63" above what they reported for the male average)
Ideal Erect Girth: 4.90" (0.40" above what they reported for the male average)
『So most of these women are probably lying because they don't want to admit that they prefer guys with bigger dicks, right?』
Stewart et al. 2009: Measure male partners of pregnant women in Australia.
Average Bone Pressed Stretched Length: 5.91"
『Maybe those women are mostly settling but they'll probably still cheat for bigger dicks?』
Well according to 3 separate studies approximately 85% of women were satisfied with or did not wish to change their partner's penis size.,, So while it's true that in around 15% of couples the woman would prefer her partner be larger or smaller, and though that is not a negligible minority, it's still rather uncommon, and that doesn't tell us how much those women care that their partner's penis isn't their ideal. As shown above in the first Prause graphic, only about a quarter of women claim to have ever had penis size be a factor in ending a relationship with a partner, which based on the average of 6 sexual partners these women report, there would be overall just under a 5% chance of penis size (too big or too small) being a factor in ending a relationship. This overall 1 in 20 chance will of course be much higher at the extremes of penis size and lower with more typical sizes. Nonetheless this suggests that while 15% of partners may have less than satisfactory sizes, it only contributes to ending a third as many relationships. Overall it's clear that women who settled for outside their ideal and then went so far as to cheat due to size incompatibility would be quite uncommon. But we can find better studies that completely remove the concern of women settling for different than their ideal.
Female Dildo Size Preferences - Informal Study: Randomly sample women on Reddit who mentioned their personal favorite dildos, then determine dimensions of each dildo from information available online.
Data Source: Female Dildo Size Preferences - Informal Study
So now we're looking at dildo preference data which is generally: free from estimation errors (such as girl inches), free from the dishonesty of self-reporting to maintain social desirability, and free from settling for anything other than their ideal preference.
When averaged, all these women's dildo preferences yield:
Insertable Length: 6.23"
Additionally, a random sampling of comparable dildos showed that women on average are not choosing larger sizes than are available, and if anything may actually prefer slightly smaller lengths and girths than are typically available.
These dildo preference results agree with the previous studies and demonstrate the consistent conclusion that the average woman's preference is just a fraction of an inch above the average length and girth of a man's erect penis.
『But aren't those lengths Non Bone-Pressed and therefore far from the average male penis length?』
Not a single study mentioned on this page uses NBP lengths, so no. Excluding the lengths of the 3D-model study which were open to individual interpretation, all of these studies' lengths fall into the same category of insertable/functional/BP lengths. And the insertable dildo lengths themselves are already a maximal estimate since people may prefer to use less than the entire insertable length of the dildo.
A broad conclusion I can offer after doing all this research on the topic of women's sexual preferences is that: of all the mature women in the world, a very small portion of them aren't sexually inclined, of the remainder a very small portion feels almost no physical sexual pleasure and can barely if at all orgasm, of the remainder a sizable minority doesn't even enjoy penetration (and even among those that do the majority still find other forms of stimulation such as clitoral and vibrational more enjoyable than regular penetration), of the remainder that enjoys penetration (people who would be inclined to use dildos) the majority place more importance on other factors such as rigidity, shape, curvature, ridges, etc. than they do on size, however they do typically have a minimum usable length and a range of girths that they prefer for better stimulation, within this group there is only a very small minority that prefers the feeling of being stretched by large girths (6-9"+ avg. girths) or stretched by deep penetration (7.5"-8"+ lengths), instead the vast majority of women prefer sizes of avg. girths within 3.5-5.5" and even though insertable dildo length is likely to be an overestimate since women only really care that a dildo is long enough while additional length may go unused, they still usually only prefer total usable lengths less than 7" and instead prefer typical penetration stimulations such as from g-spot and/or thrusting stimulation from naturally occurring male penis sizes. Furthermore, the vast majority of these women prefer the intimacy of sex with a caring lover to any dildo.
Now you might argue that surely the above statements and data can't be correct because seeing all those women in porn going crazy for big dicks is all the evidence needed to prove that a bigger dick is always better, right? But you see, porn is about as real as WWE wrestling on TV. Sure the stunts are usually real, but even the most genuine examples are still just exaggerated portrayals for entertainment purposes. So there's really no merit to using such fiction as a way to judge women's preferences, and if we're being completely honest the vast majority of women would be relieved if you didn't make the mistake of using porn as a reference for how to pleasure women, because most of what pornstars do to make it more visually arousing amounts to a reality of pretty mediocre sex for women.
As a final thought experiment for you to better understand women's penis size preferences, I'll point out that the size of the penis has almost no significance except by comparison to the size of what it is inserted into. For a couple having intercourse, the penis is only large or small in comparison to the size of the vagina. A male-female relationship where his penis is too small or too large, is just as much a relationship where her vagina is too big or too small. And just as penises come in a wide array of different sizes so too do vaginas vary in size.,,,, As such you can think of women's penis size preferences as a mirror-image of men's vagina size preferences. When you consider how vagina size matters to guys you'll probably immediately understand that while on average, a guy would prefer his partner to have a smaller than average vagina, he also really doesn't care that much how tight or deep his partner's vagina is, as long as it isn't too extreme.
It's worth mentioning that the 3D-model and dildo studies only allowed for each woman to have one size for her ideal. While this format has its merits, it is also true that each woman will likely have a range of sizes that she would consider approximately ideal. If we were to plot a heatmap of such ideal size ranges, the sizes found to be ideal would be expected to be much more diffuse. I should also point out that these heatmaps have low sample sizes so they have an appreciable margin of error even when ignoring possible biases. And with that low sample size the heatmaps are quite stochastic and represent only an instance of a small sample. A more generalizable heatmap (though still less perfect than having a very large sample size) would involve heavily smoothing the data to simulate the expected outcome of a broad population. You can see the expected smoothed distributions of each variable over the top and right axes of each heatmap.
Homosexual Men's Penis Size Preferences
There really isn't much data available to determine the penis size preferences of men who are attracted to other men, but the decades old Kinsey Study does have some data on the subject. Granted it uses nonspecific self-reported perceptions with respect to "small" "medium" and "large", so it should probably be interpreted with respect to what sizes they typically consider themselves to be, and we can use data from another study of non-heterosexual men for that. Similar to results from women, 40% of the homosexual men reported no notable penis size preference, with the remainder skewed in favor of larger sizes (much like men were skewed towards self-reporting themselves as above average).
Another more recent and more detailed self-reported study on the subject of preference for partner's penis size comes from Serbia.
Data Sources: Bjekic et al. 2018
According to the self-reported survey by Grov et al. 2010: Men who claimed to have below average penises were significantly more likely to identify as “bottoms” (anal receptive) and men who claimed to have above average penises were significantly more likely to identify as "tops" (anal insertive).
Data Source: Grov et al. 2010
Similarly according to Moskowitz & Hart 2011: Men's self-reported penis size was a decent predictor for men's sexual position top/versatile/bottom roles both in the roles they desired and in the common roles they had in actuality. Men who reported larger penis sizes were more likely to be and want to be tops, those reporting close to average sizes were more likely to be and want to be versatile, and those reporting smaller sizes were more likely to be and want to be bottoms. Among the men whose desired and actual sexual positions were discordant, penis size was a decent predictor for which sexual roles they were pushed into in reality, following the expectations from above trends (for example a larger sized ideally versatile man would be more likely to be pushed into the top role). The study doesn't provide much useful data for penis size, however they do provide data allowing for a comparison of how men's ideal positions compare with their actual positions.
Data Source: Moskowitz & Hart 2011
We can look at dildo preference data as well to see what sizes men who enjoy receiving anal penetration typically prefer.
Data Source: Male Dildo Size Preferences - Informal Study
When averaged, all these men's dildo preferences yield:
Insertable Length: 6.96"
In comparison to the same dildo study on women, men preferred on average: 0.73" more length and 0.27" more girth than women. This suggests that anal receptive men tend to have slightly higher size preferences than women. Additionally, a random sampling of comparable dildos showed that men were favoring dildo retailers that typically had appreciably larger dildo sizes available compared to those retailers favored by women.
Data Sources: Male Dildo Size Preferences - Informal Study & Female Dildo Size Preferences - Informal Study
While the differences between the preferences of men and women may seem like a lot, keep in mind that insertable dildo length is likely to be an overestimate since it only really matters that a dildo is long enough while additional length may go unused. The above studies' conclusion that anal receptive men prefer larger sized dildos than women is supported by a separate analysis of sales data which found that the insertable sextoys women prefer to buy tend to have smaller insertable lengths and girths than the sextoys men tend to buy.