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Among all mammals, man is apparently the only one who feels a kind of concern about the size of his penis. The fact that the average penis size among men is noticeably larger, longer, and thicker than the average penis size of other primates, including larger primates like the gorilla, should be good enough for men. But no, this is obviously not the case.
There are no official figures for average penis size. So measurements will naturally vary from source to source, depending on who you ask. Researchers have conducted numerous studies seeking to determine the average penis size for men. Your results provide an idea of how you measure up.
In September 1996, the Journal of Urology published a study that calculated the average penis size (length) at 12.9 cm or 5.0 inches. In December 2000, the International Journal of Impotence Research published its own study that put the average penis size (length) when erect at 13.6 cm or 5.35 inches.
Meanwhile, Lifestyle Condoms conducted its own study during spring break 2001 among college students romping in Cancun, Mexico, and its findings revealed an average penis size when erect of 14.9 cm or 5.9 inches.
Two other online penis size surveys were recently conducted and their findings are totally different from the rest: one set the average penis size at 16cm or 6.4 inches, while the other calculated the average penis size when erect at 15.6 cm or 6.1 inches.
The Lifestyles Condom study also measured average penis size (girth) when erect and found an average of 12.6 cm or 5.0 inches.
For flaccid length, the Journal of Urology put the average penis size at 8.8 cm or 3.5 inches. Several studies emphasized that the length of a flaccid penis is not proportional to its length when erect. Some studies cite cases where a below-average flaccid penis would grow up to five times its length and twice its girth when erect. Meanwhile, an above-average flaccid penis could only grow 1.5 times when erect.
One caveat here: many of these studies might not be reliable depending on the way the survey was conducted. For example, if there was a ‘self-selection bias’ involved, meaning that men could choose to be measured or not, the results are likely to be biased. Most likely, men who felt they had small penises would refrain from being measured, while those with larger penises would easily hold on to the measurement. There are no studies that have taken this self-selection bias into account.
Also, those studies that require self-report of penis size (online studies, for example) will likely have flawed results given men’s inclination to exaggerate their penis size or measure the penis incorrectly. For example, the two online studies on average penis size mentioned above reported significantly higher measurements than the other studies.