I come from an atheist/agnostic home in Europe and although my parents never ever talked to me about sex or lgbt issues and always assumed I'm straight and talked to me about boys, I wasn't all that worried about coming out to my mom at least. I didn't do it for a long time because I thought I would be divulging an aspect of my sex life they didn't need to know (somehow I figured bi = pervert, due to some internalized shit I guess). My friends have always known, though. It's never been much of a secret. After I started presenting more androgynous and girls started thinking I was gay, my mom kept telling me to get a boyfriend so my new friends would know I'm straight, I figured "I'm not omitting anymore, I'm straight up lying", so I told her and she was absolutely wonderful and smiled and said that's really cool.

I honestly still haven't told my dad, because he's been very adamant about his stance that "gayness aught to be invisible", as in, he doesn't mind them and thinks they should have their rights but thinks pride is counterproductive and why do they need to get married in a church if it's against religion and why are gay men so flamboyant etc. So I figure I won't tell him before I have a girlfriend, and when that happens I have no intention of explaining anything to be honest.

I come from a place where gay is really not a big deal though. My dad is conservative in comparison to the general population and my only problem ever has been the bi-issues (attention seeking and promiscuous, not bi at all, etc.). Which is probably why I waited 7 years to tell my mom who obviously doesn't mind. I realize I'm lucky, though, in that my family is so laid back about this that I can date women exclusively with a clear conscience and without risking any important relationships.

TL;DR out and bi always, never told my parents cause I don't have to tell them about my sex life, when I told my mom she was cool, won't tell my dad before I have a serious girlfriend (probably won't be a big deal).