Whether because of measurement error, respondent selection bias (only men with larger penises want to participate in research), or good old fashioned misreporting (i.e. lying), it seems that studies employing self-report to find the length of the average erect penis have given us the wrong answer for decades.

When researchers actually measured erect penises in the lab from representative samples of men, the average length ranged between 5.1 and 5.5 inches. Globally, the real average is probably closer to the bottom of the range.

So the average erect penis is about an inch shorter than what most men think it is. The problem with this disconnect between perception and reality is that it has prompted male dissatisfaction with their genitalia. Surveys suggest that between 45 and 68 percent of men wish they had a larger penis. Forward-thinking male sexual health expert Dr. Bernie Zilbergeld once remarked, “It is not much of an exaggeration to say that penises in [men’s] fantasyland come in only three sizes—large, gigantic, and so big you can barely get them through the doorway.”