The exact age is different with everyone just like everything else. It is typically 20-21 I believe. Same for all growth in males. I like scooter's version of measuring.
"The proper way to measure your penis is to place the rular along to top of the penis and "press" it inwards until it reaches the pubic bone. This is how MOST scientific experiments/reasearch measurements are made."
That makes the measurement come out a little longer.
