What is the average penis size ?

For most men, the size of the penis is a measure of masculinity and one's ability to satisfy another person sexually. Due to this, penis size can have a significant impact on your self-esteem and self-confidence. Having a smaller than average size penis can lead to feelings of anxiety and fear of intimacy.
Hundreds of studies and researches have been made to determine the average penis size. Here are some results:
Study #1
The Alfred C. Kinsey Institute for Sex Research
Year: 1948
Sample: 3500 white college males
Average penis length = 6.2 inches
Average penis girth = 4.9 inches
Comments: It is important to note that the information used in the survey was based on men who measured themselves. Only white males were included in the survey and they were all college students, so it did not represent a wide diversity of races or ages.
Study # 2
Durex Condoms
Year: 1980
Sample: 2,936 men from different countries
Average penis length = 6.4 inches
Average penis girth = 5.2 inches
Comments: Men were asked to measure themselves and then report their results online. The bulk of respondents were from the United States and the majority of participants were white.
Study # 3
LifeStyles Condomns
Year: 2001
Sample: 301 volunteers over 18 years old
Average penis length = 5.9 inches
Average penis girth = 5.0 inches
Comments: Each volunteer was measured by a researcher.
Study # 4
Brazilian Urologist
Sample: 150 Brazilian men
Average penis length = 5.7 inches
Average penis girth = 4.7 inches
Comments: Each volunteer was measured by a researcher.
One important conclusion is that volunteers may in fact exaggerate their own size when permitted to measure themselves.
So considering the results above, it would seem that the average erect penis measures between 5.7 and 6.4 inches in length and between 4.7 and 5.2 inches in circumference.
(note: 1 inch = 2.54 cm, 0.25 inch = 0.635 cm)