[Amnorix]

FWiW

http://www.kinseyinstitute.org/resources/bib-penis.html

Q.What is the range of erect penis length for most men?
A. 5 - 6.5 inches

Q. And width?
A. Circumference of the average man's erect penis averaged 4 - 5 inches.

(Gebhard and Johnson, 1979, p. 120). Based on original Kinsey data, 1948.

BUT:

ow did the Kinsey researchers measure penis size?
Men were asked: "How long is your penis, measuring on the top side from your belly out to the tip?" They were each given a pre-stamped card to take home, and instructed to mark the length on the card when flaccid and when erect. Approximately 2500 men participated.

Also, during interviews with over 4,000 men, the interviewer asked the subject to estimate his penis size. The interviewer would hold out a ruler (the numerals were not visible to the subject) and move his finger along it.

There was a slight underestimation of penis size, compared with actual measurements.
(Gebhard & Johnson 1979, p. 116.)

and

Penis Size

According to Gebhard and Johnson (1979), the average erect penis of males in the US is 5-7 inches and the average circumference is 4-6 inches. See Penis FAQ & Bibliography for more information.
More recent data (not yet published) indicates an average erect penis length is between 5 to 6 inches, and average flaccid penis length ranges between 1 and 4 inches.
A study of 300 men (unpublished) conducted by Kinsey Institute researcher Dr. Erick Janssen from 1989-1993 returned a mean penis circumference of 122 mm (approximately 4.8 inches).
For a discussion of recent research, and facts and myths about penis size, see "Penis Myths Debunked" at www.livescience.org.
For a discussion of the facts and myths about penis enlargement, please visit the Male Sex Questions section of our Kinsey Confidential website.

http://www.kinseyinstitute.org/resources/FAQ.html#penis