Sorry, i think a normal cock quits developing about age 16 or 18. Mine was full size at 12 or 13. Although the base of the shaft continued to get bigger with use.
15-16 aprx id say. At 20 it's definitely done growing in my opinion.
By #320350 at 14,Jun,24 03:36
I’m not sure about other guys but I can tell you that when I was just about 13 years old my cock was much bigger than the other boys. I measured 7 1/4 inches long and 5 3/4 inches in circumference. I used to be able to suck on my own cock. It has always measured the same size. It’s just thicker in circumference these days
By #7976 at 01,Sep,09 01:57
I don't know at what age it reaches full size but I can tell you that it reaches it's limits quite frequently.
The site medical officer concurs!