Most research on this question asks people to fill in a survey. This one built 343 anatomically varied men, projected them life-sized onto a wall, and had 800 people rate them. The headline everyone ran was "size matters." The finding that actually matters is what happened at the top of the scale — and the gap between how women rated the figures and how men assumed women would rate them.
What They Actually Did
The study was published in PLOS Biology on 22 January 2026 by a team from the Australian National University, Monash University, the University of Melbourne, and the University of Western Australia. It's an experimental design, not a survey — which is the whole point.
Real bodies vary in a hundred correlated ways at once. Taller men tend to differ in build; build correlates with fitness; fitness correlates with grooming and confidence. So if you show people photographs and ask what they find attractive, you can never isolate a single trait. The solution is to build the men from scratch.
🔬 The Method
The researchers generated 343 computer-generated male figures that varied in exactly three traits and nothing else: flaccid penis size (7 values from 5 cm to 13 cm), height (7 values from 1.63 m to 1.87 m), and body shape measured as shoulder-to-hip ratio (7 values from pear-shaped to V-shaped). Seven × seven × seven gives every possible combination.
The trait ranges were set to span roughly two standard deviations either side of the mean — covering about 95% of the variation a person would ever actually encounter. Each figure was shown as a short video rotating 30° left and right so raters could judge proportions properly.
Over 600 men and over 200 women took part. Some rated the figures projected life-sized onto a wall from 6.5 metres away, alone in a room; others rated scaled versions online. Women were asked how sexually attractive each figure was. Men were asked one of two questions: how jealous they'd feel seeing that man talking to their partner, or how threatened they'd feel if he picked a fight.
Nobody was told which traits were being varied.
Finding One: Body Shape Beat Everything
All three traits significantly increased how attractive women rated a figure. That part is unsurprising and has been found before.
What's worth sitting with is the ranking. Linear selection was strongest on body shape — the shoulder-to-hip ratio — with weaker though still significant effects for height and penis size.
Of the three traits tested, the one that moved the ratings most was the one you have the most control over. You cannot change your height. You cannot change your anatomy. You can absolutely change your shoulder-to-hip ratio, and it outperformed both.
Finding Two: The Ceiling
This is the part the news coverage mostly skipped.
When women rated attractiveness, the researchers found significant quadratic selection gradients on all three traits — statistical language for a curve that flattens. Bigger helped. Then it helped less. Then it stopped helping much at all.
In the paper's own framing: while taller, more V-shaped men with larger penises were consistently preferred, the benefits of further exaggeration began to plateau at the upper end of the range.
Women's ratings showed significant diminishing returns on penis size, height, and body shape. Men's assessments of the same figures showed no such plateau — the paper describes male ratings as open-ended directional selection.
Finding Three: Men Got It Wrong, In One Direction
Here is the result that should be on a poster in every locker room.
Men rating rivals broadly agreed with women about which traits mattered. They correctly identified that taller, more V-shaped men with larger penises were rated as more attractive. Men are not delusional about the direction.
But the male ratings had no plateau. Where women's curves bent and flattened at the upper end, men's kept climbing in a straight line. For women rating attractiveness, 10 of 12 estimates of non-linear selection were statistically significant. For men rating a rival's attractiveness, only 2 of 12 were.
Estimates of diminishing returns that were significant when women rated attractiveness — versus 2 of 12 when men rated the exact same figures
The authors draw the conclusion themselves: this sex difference suggests that men tend to overestimate the extent to which these traits affect female mate choice, inflating their perception of how much competition a more attractive rival represents.
❌ What men believe
Every additional centimetre keeps buying more. The scale runs upward forever and someone is always further up it than you.
✅ What the ratings showed
The curve bends. Past a point well inside the normal range, further increases bought very little additional attractiveness.
Put plainly: the anxiety is real, it's measurable, and this study measured it as a systematic error in male perception rather than an accurate read of what women want.
Finding Four: Rivals, Fights, and a Very Weak Signal
The paper's genuinely novel contribution — the reason it's in PLOS Biology and not a sex-research journal — is that it's the first experiment in any species to manipulate genital size and test whether it functions as a signal of fighting ability.
It does. Men rated figures with larger penises as more physically threatening. But look at the magnitude.
| Comparison | How much weaker |
|---|---|
| Penis size vs. height and body shape, for perceived fighting ability | 3 to 8× weaker |
| Penis size for fighting ability vs. penis size for attractiveness to women | 4 to 7× weaker |
The authors' interpretation is that penis size behaves less like a "badge of status" for male-on-male competition and more like a sexual ornament. Beards and deep voices work the other way round — they influence male perceptions of dominance more than female perceptions of attractiveness. Size doesn't. Whatever intimidation effect exists is dwarfed by height and build.
If your worry is what other men think of you, the data says they're mostly reading your height and your shoulders. Size registered, but at a fraction of the strength — and men were being asked to imagine a fistfight, which is not a situation most people are actually in.
The Limitations, Stated Honestly
We're not going to oversell this. Several caveats matter, and the authors name most of them:
- The figures were computer-generated. They were anatomically modelled and rotated for realism, but they are not photographs of men, and no figure had a face, a personality, a voice, or a job.
- The penises were flaccid. The authors note that flaccid length correlates positively with erect length, and speculate that erect figures might show even stronger effects — but that's an untested guess, not a finding.
- Attraction here means a rating on a 7-point scale after four seconds of video. It is not a relationship, a date, or sex.
- Culture wasn't isolated. The authors are explicit that mate preferences are shaped by cultural norms, that the in-person female sample was mostly white, and that cross-cultural work is still needed.
- Online and in-person surveys disagreed in places. Notably, the online surveys failed to detect the plateau on height that the life-sized version found — the authors argue small on-screen images can hide diminishing returns entirely, which is a quiet indictment of a lot of previous research in this field.
What survives all of that is the comparison, because both sexes rated identical stimuli under identical conditions. The gap between how women rated the figures and how men predicted women would rate them isn't an artifact of the method. Both groups were looking at the same wall.
So Where Do You Actually Sit?
The study's trait range covered about 95% of natural human variation. Almost everyone reading this is somewhere in the middle of it — on the flat part of that curve. Find out exactly where, using clinical measurements from 15,521 men.
Get Your Real Percentile →The Takeaway
A well-designed experiment with 800 participants found that penis size is one of three traits influencing perceived male attractiveness. It ranked third. Body shape ranked first. And the benefit of more flattened out inside the normal range.
It also found that men systematically fail to see that flattening. They think the line keeps going up. They rate rivals as more threatening than women rate them as attractive.
If you've spent years assuming there's an unreachable tier of men who are winning on a scale you can never climb — this study says that tier is largely something men invented while looking at each other. The women in the experiment stopped scoring higher a long way before the top of the range.
And the trait that actually moved the needle most was your shoulders.
Sources
- Aich U, Tan C, Bathgate R, Blake KR, Capp RCS, Kuek JC, Wong BBM, Mautz BS, Jennions MD. "Experimental evidence that penis size, height, and body shape influence assessment of male sexual attractiveness and fighting ability in humans." PLOS Biology, 2026; 24(1): e3003595.
- Mautz BS, Wong BBM, Peters RA, Jennions MD. "Penis size interacts with body shape and height to influence male attractiveness." PNAS, 2013; 110(17): 6925–6930. (Source of the original figure set.)
- Veale D, Miles S, Bramley S, Muir G, Hodsoll J. "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, 2015; 115(6): 978–986.
- Ponchietti R, Mondaini N, Bonafè M, et al. "Penile length and circumference: a study on 3,300 young Italian males." European Urology, 2001; 39(2): 183–186. (Source of the trait ranges used in the 2026 study.)