Here the data in cm:

So the average penis length is 15.64 cm.
The average girth is 12.28 cm.

More recent studies have produced the following results:
A sample of 60 men studied by researchers at the University of California at San Francisco determined that the average size of their erect penises was 13 cm long and 12.5 cm in girth. A Brazilian urologist who measured 150 men reported that the average size of their erections was 14.5 cm long and 11.9 cm in girth.