“It is not much of an exaggeration to say that penises in (men’s) fantasy land come in only three sizes – large, gigantic, and so big you can barely get them through the door” (Zilberberg, 1978)

But what is a ‘normal’ size penis? Is there a difference between what men think, that the average length is 15.2 cm (6 inches), and reality? That’s the topic of this blog. It is based on a literature review.

The length of the penis has been researched many times and in three different ways. In one way the erect penis was measured. Measured either by 1) the men themselves or 2) a researcher, and 3) the  stretched flaccid penis length was measured by a researcher.


Self-reported erect length (10 studies):

  • Range between 15.8 and 25.4 cm (6.2 inch – 10+ inch)

Researcher measured erect length (9 studies):

  • Average length between 12.95 and 13.97 cm (5.1 and 5.5 inch)

Researcher measured stretched penis length (22 studies)

  • Mean length (n=13.719)= 12.98 cm (5.11 inch)

(problem: underestimation of erect length)

The difference between self-reported and researcher measured length is substantial. This might be due to several problems occurring when men are asked to measure themselves: volunteer bias and social desirability bias. Men would like to have a longer penis.

In one study men (n=1661) were asked to measure their penis with the objective to properly fit a condom and not to research the length. The mean self-reported length of the penis was 14.15 cm (5.57 inch), so quite a difference with the mean self-reported length found in the studies focusing on length.

So I think we can conclude that there is a substantial difference between what men think and the reality. If we get a question regarding the average size of the penis we can now give a reliable answer. The average size lies between 12.95 and 13.97 cm!



Bruce M. King (2020): Average-Size Erect Penis: Fiction, Fact, and the Need for counselling, Journal of Sex & Marital therapy, DOI: 10.1080/0092623X.2020.1787279.

Zilberberg, B. (1978). Male sexuality: A guide to sexual fulfillment. Boston. Little Brown.

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