When to come out?

I am 13 years old and gay, I'm wondering when to come out? I'm not 100% SURE sure how my parents act towards gay people but, my dad refers to "the gays" and makes jokes some of the time (sometimes towards my dog i know its weird but anyway). My mom REALLY didn't like when they legalized marriage (don't like just saying "gay marriage"). What should I do and when/should i come out yet?