I don't think there is a fixed age when you need to come out. In my opinion, coming out is a matter of accepting who you are bothered by the fact that the person(s) you want to tell take you for someone you are not! I personally came out to my best friend when I just couldn't keep it inside anymore... it was too much! I would be perfectly fine right now if my friends knew, but I'm still afraid of my parents finding out about it.
So, take your time, come out only when you're ready, and be careful to whom you come out (like... avoiding homophobic people if possible). Cheers!
-Mihai