I agree with Donk. I measured alot between the ages of 15 and 18 and I grew between 3-4 inches longer then and I had a real growth spurt of thickness around 17 years old. I did grow an inch longer in one summer when I was 17. I know cuz it put me over 10 inches and the next year an a half I grew to 11.5 I lost alot of girl friends around that time too.