Empirically, you're only old enough when you actually do it. That's circular logic in my book...

I was 13 and it was great -- the guy is still my best friend (with benefits) and I am now 26 (almost 27). Was I ready -- no...but I knew that I cared about THIS guy and that I needed to participate in this "rite of pasage." I was curious about being with a man and I trusted him to treat me well.

It's not just a emotional/lustful decision... Think about what you're trying to accomplish by having sex. Closeness with another person? Maturity? Pregnancy (please no)?

And then decide if that reason warrants your actions.

Best of luck...

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Life is too short not to love and be loved....preferably multiple times in one night.

I think men talk to women so they can sleep with them and women sleep with men so they can talk to them. ~ Jay McInerney