Sex Ed

How Do People’s Beliefs About Average Penis Size Match Up With Reality?

May 16, 2016 by Justin Lehmiller

If you had to guess what the average penis length is, what would you say? A medical organization in the United Kingdom, DrEd, recently asked this question of 2,121 people from ten countries. Here’s what they found:

Overall, women estimated the average penis length at 13.8 cm (5.4 in). By contrast, men estimated it at 14.1 cm (5.6 in). Thus, men appear to think that the average penis is slightly longer than women do.

However, it seems that both men and women think the average penis is bigger than it really is. Although we can’t say with certainty what the average penis size is, the most definitive data we have comes from a recent review paper published in the British Journal of Urology International in which scientists looked at the results of 20 studies that included measurements of 15,521 penises from around the world.

In this sample, the median (50th percentile) penis length was 13.1 cm (5.2 in). This is a little shorter than the average guess in the DrEd survey, but still reasonably close.

However, it’s quite a bit shorter than what people say the ideal penis size is. In the DrEd survey, women rated the ideal penis length as 15.8 cm (6.2 in), while men rated the ideal penis length as 16.6 cm (6.5 in).

Given the sizable gap between perceived average and ideal penis length, it is probably not surprising to see that many men in the DrEd survey reported being dissatisfied with their penis size and, further, that their penis size had a negative effect on their sexual confidence.

Interestingly, there was quite a bit of variability across countries when it came to estimates of perceived average penis length and ideal penis length. The relative difference between these numbers varied a bit, too.

As you can see in the figure below, average perceived penis length was longest in Poland and Austria, but shortest in France and the U.K, with the U.S. coming in toward the middle.

The biggest discrepancy between perceived average and ideal penis length was in the U.S., where the gap was 2.7 cm (1.1 in); the smallest discrepancy emerged in the Netherlands, where it was 1.1 cm (0.4 in).

In thinking about what all of this means, it’s important to keep in mind that people might not be very good at estimating penis length off the top of their heads. Thus, it could very well be that people were overestimating here because they haven’t really stopped to measure a penis before—and even among those who have, there isn’t necessarily a standard way of measuring length (let’s just say that some techniques are more generous than others).

However, these results are consistent with other research finding that men think women prefer longer penises than they really do, as well as research suggesting that a lot of guys aren’t happy with the size of their penises.

To learn more about research on penis size, check out these articles:

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Photo Credits: 123RF (image), DrEd (figures)

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Written by
Dr. Justin Lehmiller
Founder & Owner of Sex and Psychology

Dr. Justin Lehmiller is a social psychologist and Research Fellow at The Kinsey Institute. He runs the Sex and Psychology blog and podcast and is author of the popular book Tell Me What You Want. Dr. Lehmiller is an award-winning educator, and a prolific researcher who has published more than 50 academic works.

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