16 is the average age, but you should just wait until you've fallen in love, whichever age that should be. Don't have sex just to have sex. It's better when you love the guy anyway.
Everyone is different, so when one person says you should wait, they may just be speaking from their own experience. From my experience, I'm 16 and have had sex with my boyfriend twice, and I really don't see anything wrong with it because it was great and it enhanced our relationship, rather than complicated it.
Whenever you're ready, to make a long story short.