Erectile Dysfunction
8 minute read

Average Penis and Erection Size: What's Normal?

Written by
Reviewed by
Dr Ai Nhi Bui

Most men, at some point, have wondered or even asked, "What is the average penis and erection size?" You may have also asked this question. A study in the BJUI found that the average flaccid penis length is 9.16 cm while the average erect penis length is 13.24 cm.

Deep down, everyone wants reassurance that they are normal. However, normal and average are very different. A wide range of penis and erections sizes are normal. In contrast, an average is a single number with half of men above and half below this marker.

An average depends on what population is chosen, how accurate the measurements are and how many men are surveyed. Measurement errors and relying on self-reported data have led to a lot of misinformation on the internet on the average penis and erection size.

Self-reported data tend to be inflated, leading many men to feel inferior, resulting in decreased self-confidence. Many men may feel anxious about how their penis and erection size may sexually satisfy themselves and their partners. Anxiety about sexual performance can lead to erectile dysfunction and premature ejaculation. It can become a vicious cycle.

That’s why we’ve reviewed the scientific studies to find out once and for all what is the average penis size - to put all of our minds at ease. 

Researchers systematically reviewed all the studies available on penis size and erection size to gather more accurate data. They only included studies in which measurements were made by a healthcare professional using a standard procedure. Each study had to include a minimum of 50 participants. Overall, the study included 15,000 men.

There are two important points here: the data is not self-reported, and the measurements were done using a standard procedure. Consider reading How to Measure Your Penis Correctly to ensure your measurements are accurate.

Research on Average Penis Length and Girth

Here is what the study reported in BJUI found:

Average flaccid penis length: 9.16 cm

Average stretched penis length: 13.24 cm

Average erect penis length: 13.12 cm

Average flaccid penis circumference: 9.31 cm

Average erect penis circumference: 11.61 cm

Even if it consisted of 15,000 men, an average number in a given population could only provide so much information. It does not answer the question, what is normal? Normal is a wide range of measurements. To get a more accurate idea of what is normal, you need a little math.

A More Accurate Measurement of What is Normal

Feel free to skip the explanations on standard deviations in the next paragraph and jump right to the table. If your measurements are bigger than the smallest number in the "smallest number column" and smaller than the largest number in the "biggest numbers" column, you meet the definition of normal.

Standard deviations (SD) give information on the amount of variance in penis size in the population. If the standard deviation is low, you would expect most men to have penis and erection sizes close to the mean. Likewise, if the standard deviation is high, there is a wide range of lengths. In a normal distribution, approximately 68% of men would be within one standard deviation of the mean, 95% of men are within two standard deviations, and 99% are within three standard deviations.

Using the information from the study, you can determine the upper and lower bounds of each. Notice that the difference between the larger and smaller numbers becomes greater as you add more standard deviations. 

The average penile and erection length in a study of over 15,000 men (in centimeters):

The Discrepancy Between What Men Think the Average Penis Length Is and the Data

When men were asked what they thought was an average penis and erection size, their answers were pretty far off from what researchers found. Most men believe that the average length of an erect penis is greater than 15.24 cm. If you go back to the table, you see that what most men think is average is actually in the "biggest numbers" columns.

Why the discrepancy? If you asked a hundred men to measure their penis size and erection size, how would they do it? Would a self-confident man who feels he is well-endowed or a man who is anxious that he does not quite measure up be more likely to report their data? If a man knew he would report his penis size and erection size, would he err on the generous or the conservative side with the measurement? It's the same situation as women comparing their looks to air-brushed models and feeling self-conscious every time! Men are taught that it is socially desirable to have a bigger penis and a larger erection, just like women think the air-brushed look is socially desirable. Social desirability bias also contributes to inaccurate measurements.

Overall, because men have been given inaccurate information, researchers found that most men underestimate the size of their penises compared to other men. This misconception can have serious implications for men seeking penile lengthening surgeries. Researchers found that most men seeking penile lengthening surgeries, a risky surgical procedure, had normal penis sizes. This misconception can also lead to sexual anxiety, avoiding sex, and having problems with erectile dysfunction and premature ejaculation when they do have sex.

Are There Different Types of Penises?

A man's penis can come in different shapes, all of which are normal. All penises have a shaft with a head that tends to be wider than the shaft. An erect penis may curve upward or downward. It may bend to the side slightly or be straight. All of these shapes are normal.

A thicker fat pad in front of the pubic bone, fluid retention, shorter ligaments, or complications after a circumcision can make the penis appear much smaller in some men. This is called a buried penis. If you have a buried penis, your penis is actually longer than it seems. If you have a buried penis and have difficulty urinating or with sexual function, talk to your doctor.

A micropenis is an abnormally small penis. By definition, it is a penile length that is more than 2.5 standard deviations below the mean. For an adult, a stretched penile length of less than 9.3cm would meet the criteria. Heredity and low production of hormones may be contributing factors.

If your self-measurement of your penis length is less than 9.3cm, don't draw any conclusions based on this measurement. This cut-off is based on health professionals using a standard measurement technique. If you had a micropenis, you would almost certainly have other signs and symptoms secondary to decreased testosterone levels.

Does the Average Penile Length Vary by Country?

Knowing that genetics and hormone levels influence penis and erection size, you may wonder whether the average penis and erection size varies by country. 

Yes, it does. Average height and average weight also vary by country. Just like average weight, which women watch like a hawk, these numbers mean little. Since you are curious, here's what researchers found.

Over all countries, the average penis length reported by WorldData was 13.58cm, which correlates well with the data in the study reported in BJUI, which found that the average stretched penis length was 13.24 cm.

In Australia, the average erect penis length is 14.46cm. The shortest erect penis length by country was reported from Cambodia at 10.04cm. The longest was reported from Ecuador at 17.61cm.

Do Penis and Erection Size Matter?

Research shows that 68.3% of 200 men surveyed had concerns about their penis size. This fact should not be a surprise to anyone. Unlike other physical parameters, diet, pills, and exercise regimes do not affect penis or erection size, leaving many men at a loss on what to do. Half of men have the misconception that they can change their penis size in ways that do not involve surgery.

Much of the anxiety and dissatisfaction men have with their penis size result from what they think women want.

In a large internet-based study of 52,031 heterosexual men and women, 85% of women were satisfied with their partner's penis size, while approximately 45% of men thought their penis was too small. In another study of 170 women, 55% of women found the length of the penis unimportant, and 22% of women felt it was very unimportant. This means that 77% of women felt that penis size was unimportant!

When researchers used 33, 3D models of penises and asked women to choose their size preferences for long-term and one-time partners. Women preferred a larger penis size, particularly circumference, for a one-time partner as compared to long-term partners. Overall, women chose a penis size slightly above average (16.0cm length, 12.2cm circumference).

Your perception of your penis size affects your confidence and your body image. If you are self-conscious about the size of your penis or the size of your erection, you may experience erectile dysfunction (ED) or premature ejaculation (PE).

One study in 2010 states that 40% of Australian men experience ED. Another study from 2017 cites that 61% of Australian men age 45 and older are affected, and a third study shows that 21% to 31% of Australian men experience premature ejaculation. These sexual health issues affect a large proportion of the population.

ED & PE treatment online with Rosemary Health

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