Patrick Carroll, MD Medically reviewed by Written by Our Editorial Team Last updated 3/28/2019

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Worried about your penis size? Relax, you’re not alone. At some point, just about every guy has wondered how their penis stacks up compared to the average.

Like many aspects of sex and anatomy, penis size is a subject that creates distorted perceptions of what’s “normal.” Most studies of penis size around the world show that the average penis size is, to put it simply, not quite as big as people may think.

According to a review of study data by researchers at King’s College London, the average flaccid penis measures 3.6 inches from base to tip.

When it comes to the circumference (the circular measurement around the penis), the average man is about 3.7 inches soft.

Erect, the average penis is about 5.2 inches in length, with an average circumference of about 4.6 inches.

Not quite what you’d expect, right? From harmless bragging to porn-induced expectations about penis size, there are numerous factors that contribute to the belief that the average man’s penis is, well, bigger than the real average.

In this guide, we’ll look at some more of the data behind the average penis size. We’ll also look at whether or not size (or lack of size) is really an issue that you should spend your time thinking about.

“Am I Normal?” The King’s College Penis Size Study

Penis size is a common source of anxiety for men. Because of unrealistic expectations about what is and isn’t normal perpetuated by media and pornography, a surprising number of guys worry about whether or not their penis is big enough.

In an effort to help clinicians dealing with Body Dysmorphic Disorder and men feeling anxious about their size, researchers at the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King's College London completed a thorough review of study data about penis size.

The review, which can be viewed online here, is currently the most comprehensive study available on penis size, drawing from a total of 20 studies with more than 15,500 participants.

As stated above, the researchers found that the average penis size -- using a sample of more than 15,500 men -- was 3.6 inches (9.16 cm) when flaccid and 5.2 (13.12 cm) inches when erect.

The study data should come as a relief to many men, confirming that the “six inches” average that’s often promoted in media or casual conversation isn’t even close to the reality of penis size.

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Real Study Data vs. Public Perceptions of Penis Size

What’s particularly interesting is the difference between the real data on penis size and the perceived average penis size people report when surveyed.

In a survey conducted by UK company Health Bridge Limited, researchers asked people to state what they believed the average penis size was. The survey featured men and women, drawing data from thousands of people located throughout Europe and North America.

The average length given by participants varied by country, with Poland reporting the biggest perceived average penis length at 6.18 inches (15.7 cm). Austria, Italy, Germany and the United States all featured estimates well above the real average, at 6.14 inches (15.6 cm), 6.02 inches (15.3 cm), 5.83 inches (14.8cm) and 5.63 inches (14.3 cm), respectively.

For the most part, survey participants overestimated the average penis size by about half an inch to one inch (1.3 to 2.5 cm). Of the 10 most widely surveyed countries, only the UK guessed an average size below the real average, estimating that the average erect penis is 4.88 inches (12.4 cm).

The survey data shows that most people overestimate the average erect penis size, often by a significant amount -- a fact that can create anxiety, frustration, and insecurity for many men.

Does Penis Size Really Matter?

In the same survey, women were asked how important penis size was to them in a partner. The survey respondents were given three options to choose from: very important, somewhat important and not important.

The overwhelming majority of female survey participants, 67.4%, said that penis size was only somewhat important to them -- that it wasn’t a major concern or of overriding importance in their choice of partner.

Another 21.4% of female participants said that penis size wasn’t important at all. In fact, only 11.2% of women that responded to the survey said that penis size was very important to them when choosing a romantic partner.

Scientific study data also seems to support the idea that penis size just isn’t a major issue for most women. In a 2015 study of penis size and sexual attraction (all participants were residents of California, 18-65, sexually experienced) , researchers found that only 27% of women had ended relationships, in part, due to a difference between their preferred penis size and the size of their partner’s penis.

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Should You Worry About Penis and Erection Size?

Certain aspects of your body can be changed through things like diet, exercise, medication and grooming. Penis size -- save for factors such as erection quality -- isn’t one of them.

Combine this with the fact that the vast majority of people overestimate the average penis size and that the vast majority of women simply don’t care about penis size, and it quickly becomes clear that the best approach is to not fret too much about the size of your genitals.

Instead, a better approach is to focus your time, energy and effort on improving the aspects of your sexual performance and appearance that you do have control over, from preventing hair loss and improving grooming to increasing your erection quality, and most importantly, taking care of yourself.

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