I was going to say 17-20, but then notice that your skin is free of acne... lol so more like 19-21 and that's not so bad... I think if you got a shorter hair cut instead of a "sk8ter" cut, it would help... but you have a "pretty boy" face. You're really cute actually, but that's prob not what you want to hear...
I say don't worry about it... You only look a few years younger, and it'll pay off later... plus, it'll force people to really get to know you for you, not for what you look like...but for who you really are. "The people who mind don't matter and the people who matter don't mind"
17. I think its your hair style that makes you look younger, however you also seem to have a "babyface" which a lot of girls go crazy for.. I say find the girl that likes you for what you are, not what you think she wants. Embrace what you have, and forget what you don't. If you got it, flaunt it.
In all honesty I would have to say about eighteen. Really though, its not a big deal. I know it may seem like it now, but try not to worry what other people say. Besides, I think you're a very cute guy, and with time the right girl will come. :] Good luck!
looking younger isn't a bad thing. my friend had a beard in 7th grade and he looks like he's 30 now and he's only a sophmore in college. rather look like that or younger? besides you can hang around the high schools and pick up girls ahaha just kidding, that illegal. but yeah whatever man, I'm 19 you look older than I do