Is there any way I can know whether my penis will stop growing?

Hi Guest,

You are NORMAL but you are also bigger than average for an adult male - 5.1".

Yes, some guys are bigger.  Some are smaller.  It's all normal.

Your penis could grow into your early 20's.  We don't know how much, if any, more growth to expect.  It's part of your DNA.

Hope it helps.