The Average Penis Size, According to Science (And Nobody Told Me This When I Was Single)

I have questions. Scientific ones. I spent years as a single woman with a completely unrealistic preference for eight inches — and nobody corrected me.

The Average Penis Size, According to Science (And Nobody Told Me This When I Was Single)

I have questions. Scientific ones.

I spent years as a single woman with a completely reasonable, totally normal, absolutely not-at-all-unrealistic preference for eight inches.1

Nobody corrected me. Not one friend, coworker, or a single one of the approximately ten thousand romance novels I was reading at the time.2 Everyone just let me walk around with those expectations like they were based in reality.

They were not based in reality.

I built a platform that sells romance and erotica because I love these books with my whole heart. And last week I fell down a PubMed rabbit hole at midnight and discovered that I - along with (I suspect) many of you - have been working from profoundly incorrect data.3

This is my formal debrief. I'm bringing you all with me.

📊 Before reading this post, what did you believe the average erect penis size was?

A.Under 5 inches (you have done the research, I respect you)
B.5–6 inches (a reasonable human guess)
C.6–7 inches (same as me, we're going to be fine)
D.8+ inches (we need to talk, and also I was you, no judgment)

Pick one ↑

First, the Data. Because I Have Had a Week.

Scientists have been measuring penises for decades. This is a real job that real people have.

The most comprehensive study to date - a 2015 meta-analysis published in BJU International4 that measured 15,521 men (with a tape measure, by a professional, not over text at 2am) - found that the average erect penis is 5.17 inches long and 4.59 inches in circumference.5

Five. Point. One. Seven.

I need you to understand that I stared at that number for a long time.

A 2023 meta-analysis out of Stanford and Milan's San Raffaele University6, which looked at 75 studies and 55,761 men across multiple decades, confirmed a similar number: 5.49 inches erect, clinically measured. Same study also found that average erect penis length has increased 24% over the past 29 years globally.7

Nobody knows why. Scientists are genuinely concerned. I don't know how to feel about it either. I'm going to file it under "things that are happening" and keep going.

Here's where it really gets interesting: when men self-report their measurements, the average jumps to about 6.2 inches. Researchers have a clinical term for this.8 It's called lying. I have a personal term for it too but I'm trying to keep this classy, ok?

📊 A man measures himself and reports the result. How much do you trust that number?

ACompletely. Men are known for their humility and precision, especially those found in D.C. these days. In houses painted white.
BSomewhat. He probably rounded up to the nearest inch.
CNot at all. That tape measure was not held straight and we both know it.
DI require a notarized third-party measurement.

Pick one ↑

The Volunteer Problem (Or: Who Signs Up for a Penis Study)

Science also has a sampling problem here.

When researchers ask for volunteers to participate in studies measuring penis size, who raises their hand? Men who feel confident about what they're bringing to the table.9 Men who are not confident are, statistically, at home. Not raising their hand.

The one guy who volunteered

The one guy who volunteered.

This is called volunteer bias. It means that even the clinically-measured studies probably skew slightly large. The real average is likely toward the lower end of that 5.1-5.5 inch range.

This is statistical fraud perpetrated against anyone who has anything to do with a penis.10

And it's steeped in our culture, right? Porn optimizes for visual spectacle.11 Locker room culture rewards exaggeration. I mean, nobody in the history of heterosexual culture has ever bragged about being average. The brief eventually reached romance authors, who — being very good at their jobs — delivered exactly what readers called for.

💬 The brief we handed authors

"Make him impossibly large." ✓ Done.
"She'd never taken anyone his size." ✓ Done.
"He barely fit." ✓ Done.
"She gasped when she saw him." ✓ Done. (This one holds up, actually. Surprise is valid.)

We asked for this. They delivered. Now science is here to audit the brief and I, personally, am not okay.

What Women Actually Want (This Is Where I Had To Lie Down)

A 2015 UCLA study12 - I cannot stress enough how much I respect these people - gave 75 women 3D-printed penis models in various sizes and asked them to select their preferences for long-term partners versus one-time encounters (we call them casual hookups and one-night stands, and yes we have stories for that).

The models were blue.13 Scientists 3D-printed blue plastic penises, handed them to women, and said "pick your favorite." This is peer-reviewed research. This is science. (I can't even)

The preferred size for a long-term partner: 6.3 inches long, 4.8 inches around.

For a one-night stand: 6.4 inches long, 5 inches around.14

Women do prefer slightly above average. But 6.3 inches is not eight inches. It is not the forearm situation I had apparently been holding out for. It is a modest, achievable, deeply human 6.3 inches...and I spent my entire twenties being unreasonable.15

Also: 71% of women in a Psychology Today survey16 said men overemphasize the importance of penis size. Women care more about width than length. Women care more about what someone does with what they have than the measurement itself. This information has been available for decades. I found out on a Wednesday at midnight. (I'm fine)

The G-Spot Is 2–3 Inches In. I Also Found This Out On Wednesday.

The G-spot - the area most associated with internal orgasm for women who experience them - is located approximately 2–3 inches inside the vaginal canal.17

Two to three inches.

The average flaccid penis is 3.4 inches long.18

I will give you a moment.19

Me, processing

Me, processing.

The vaginal canal, when unaroused, is approximately 4 inches deep. When aroused, it expands to accommodate up to 7 inches. Which means that above a certain point, additional length is not adding stimulation. It is just... traveling. Into a place where there are no nerve endings cheering it on.20

I spent years thinking the goal was more. The goal, it turns out, was present. Attentive. Paying attention to the actual geography of the situation rather than logging personal bests.

Nobody told me this. (I am telling you now. I'm sorry it took so long.)

So How Did We All Get Here?

Porn. Locker rooms. A sex education system that was too embarrassed to be useful.21 And a cultural agreement that male ego was more important than female accuracy.

Romance didn't create this mythology. Romance inherited it and ran with it beautifully, because underneath the numbers is something that's actually true - the fantasy of desire so consuming it's almost too much. It's not about inches. It's about intense love and eros, and about being chosen by someone.

Romance understood that assignment perfectly.22

The data is clear: technique, attentiveness, communication, and what happens outside of penetration matters more to female sexual satisfaction than any measurement.23 Most women don't orgasm from penetration alone regardless of the equipment involved. This is established science that I, a grown adult woman who built a platform dedicated to female desire, found out on a Wednesday night in February.

I'm not embarrassed. I'm definitely a little pissed off, and a lot radicalised. There's a difference.24

📊 After reading all of this, your primary emotion is:

AVindicated. I knew something was off.
BBetrayed. By the culture, by the mythology, by no one in particular.
CRetrospectively exhausted on behalf of my past self.
DSending this to someone right now. They know why.

Pick one ↑

The Part Where I Recommend Books (Having Now Recalibrated)

I built Theo Reads because I love these stories. I love them more having thought about what they're actually doing - which is giving desire a shape, a language, a place to live.

The fantasy isn't wrong. The mythology around what the fantasy means was just off. Now we know. We're all better informed and the books are still excellent.25

At Theo Reads we have everything: the dark romance hero with the alarming dimensions and the intensity to match, tagged clearly so you know exactly what you're walking into. And the messy, funny, filthy story where the sex is extraordinary because of attention and chemistry and someone who actually shows up - also tagged clearly, also available, also excellent.

You deserve options. You deserve information. You deserve a platform that treats you like an adult who can handle both a good fantasy and a PubMed citation in the same evening.

That's why this place exists.26

Ready to find your book lover?

Your first paid story is on us.

Take our 30-second quiz →

Footnotes

  1. 1 A preference held with deep conviction and absolutely zero empirical basis. I have since conducted a review of the literature. The literature has opinions.
  2. 2 The ten thousand figure is approximate. A more conservative estimate would be eight thousand. Neither number changes the conclusion, which is that I was badly informed for a very long time.
  3. 3 The rabbit hole began, as all the important ones do, with an innocent Google search I will decline to specify further. It ended at 2am with three browser tabs, two empty coffee cups, and this post.
  4. 4 Veale et al. (2015) — "Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15,521 men." BJU International, 115(6), 978–986. The title "Am I Normal?" is doing a lot of emotional work in four words. The answer, per the data, is: probably yes, and also you have been lied to.
  5. 5 The 95th percentile was 6.3 inches. I'm not saying anything. I'm just saying.
  6. 6 Belladelli et al. (2023) — "Worldwide Temporal Trends in Penile Length: A Systematic Review and Meta-Analysis." World Journal of Men's Health, 41(4), 848–860. Stanford. On a penis study. I need this on a building.
  7. 7 This 24% increase over 29 years is real, peer-reviewed, and genuinely unexplained. Leading theories include endocrine disruptors, environmental exposures, and methodology changes across studies. No one has ruled anything out. Scientists are, to repeat, concerned. I have filed this under "things that are happening" and moved on.
  8. 8 The clinical term is "socially desirable responding," which is academic for "lying in a direction that flatters you." I prefer the shorter version.
  9. 9 Participation was, in most cases, entirely voluntary. Draw your own conclusions about who showed up.
  10. 10 I have considered whether anyone could be held liable for this statistical situation. I have decided the correct response is a blog post.
  11. 11 Herbenick et al. (2014) — "Erect penile length and circumference dimensions of 1,661 sexually active men in the United States." Journal of Sexual Medicine, 11(1), 93–101. Self-measured. In a penis study. The numbers came out larger. Nobody is surprised.
  12. 12 Prause, N., Park, J., Leung, S., & Miller, G. (2015). “Women’s Preferences for Penis Size: A New Research Method Using Selection among 3D Models.” PLOS ONE, 10(9). The 3D print files were made publicly available by the authors. I am choosing not to think about what anyone did with that information.
  13. 13 The blue color was chosen to minimize racial skin-color cues. This is methodologically sound and does not make the image of a table full of blue plastic penises any less extraordinary. Science contains multitudes.
  14. 14 The difference between long-term and one-night-stand preferences was 0.1 inches in length and 0.2 inches in circumference. Lever, J., Frederick, D. A., & Peplau, L. A. (2006). “Does size matter?” Psychology of Men & Masculinity, 7(3), 129–143. I have made of this gap: not much.
  15. 15 I would like to formally apologize to several people from my past who were, statistically speaking, completely normal. You know who you are. I did not, at the time, know what I know now. I hope you are well. I hope you have also found this research.
  16. 16 The survey sample was 52,031 heterosexual adults. That is not a rounding error. That is a committed research team with a very specific vision. Lever, J., et al. (2006), ibid.
  17. 17 Darling, C. A., Davidson, J. K., & Conway-Welch, C. (1990). “Female ejaculation: Perceived origins, the Grafenberg spot/area, and sexual responsiveness.” Archives of Sexual Behavior, 19(1), 29–47. Also: Jannini, E. A., et al. (2010). “Female orgasm(s): One, two, several.” Journal of Sexual Medicine, 7(2pt2), 821–827. This has been in the literature since 1990. I found out in 2026. The education system and I will be having words.
  18. 18 Veale et al. (2015), ibid. Yes, the same study. They measured everything. Flaccid, stretched, erect, circumference. These people were thorough and I respect the commitment enormously.
  19. 19 Take as long as you need. I took about four minutes. Then I made another coffee. Then I switched to tequila because I could not even with this data. Then I wrote this post. The timeline is what it is.
  20. 20 “No nerve endings cheering it on” is a lay interpretation of established anatomical data and should not be taken as formal medical advice. It is, however, accurate.
  21. 21 Carroll, J. S., et al. (2008). “Generation XXX: Pornography acceptance and use among emerging adults.” Journal of Adolescent Research, 23(1), 6–30. The abstinence-only movement gave an entire generation of adults the following sex education: don’t. We then sourced the rest from available materials. The available materials were, it turns out, not a representative sample.
  22. 22 I tried four other ways to end that paragraph. This was the least insufferable. You’re welcome.
  23. 23 Frederick, D. A., et al. (2016). “What keeps passion alive?” Journal of Sex Research, 54(2), 186–201. Also: Dodson, B. (2002). Orgasms for Two. Harmony Books. Also: Zilbergeld, B. (1999). The New Male Sexuality. Bantam Books. The research on this is extensive, consistent, and has apparently been sitting in libraries waiting for someone to tell us. I will write a separate post. I need to lie down first.
  24. 24 Radicalised: (adj.) having developed a commitment to systemic change following the acquisition of information that should have been available much, much earlier. At midnight. After tequila. See also: this blog.
  25. 25 They were always excellent. The data does not change the books. The books are fine. We are fine. Everything is fine.
  26. 26 This is the part where a lesser platform would say “you deserve options, you deserve information, you deserve a platform.” I edited that out. You’re welcome again.