What’s the Average Penis Size?

What’s the average penis size?  While many studies on penis size have been conducted, results vary from study to study.  According to Wikipedia, the average penis size is approximately 12.9-15cm (or 5.1-5.9 inches) in length when erect, with the typical girth being 12.3cm (4.85 inches).
Mean Erect Penis Length By Age:
SizeSurvey.com has conducted a penis [...]