There really ISN'T an average penis size for a 17 year old, because no one goes around asking 17 year olds how big they are. See the chart at the link below for the average size of an ADULT penis. According to the chart, average for an adult male is between 5 and 6 inches. Regardless, there's nothing you can do to make it any bigger anyway. It's all controlled by genetics. You may end up being 5" or 6" or 7"...who knows. Either way, just be happy with whatever you have. Having a big penis does not make you a better man or a better lover, knowing how to do all the "OTHER THINGS" for a girl (kissing, touching, rubbing, licking - in ALL THE RIGHT PLACES) is what will make you a better lover..and THOSE are things that you can do something about.