My parents were divorced when I was only 3 years old. My mother told me that when I was in my early 20s, my father asked if I was homosexual, because I never seemed to have a girl friend and spent most of my time on things to do with cars, and many of my friends were homosexual. If truth be told, I was far too busy "discovering" the world to be wasting time on girl friends. I loved theatre, so many of my friends were indeed "gay", both male and female.
Eventually, I started to find female companionship quite rewarding, especially if they could fix a car, help out in a photographic dark room, or handle a screwdriver.
Then I discovered they had another trick up their sleeve (or was it skirt?) and blew my father's doubts well away.
So, be patient. He's still exploring the world and choosing what he likes.

I think asking would be a bad idea. Show him through your actions and words that you aren't homophobic, he will feel safe telling you if and when it is time to.

Great mom, que sera sera. ...raging 16 year old hormones inside us guys is no time for self reflection when we parade school halls every 49 minutes between classes & gym & such....bumping into padded bras & itchy jock straps is stimulation enough for our sons to deal with. ...media is full of OK 2 b gay and an Atheist mom surely is not sending any child to hellfire Adham&Ewe lecture halls called churches. ....having 4 hockey players in the house is totally bonding time with a cool cool mom tidying up behind them. ....it's not about looking at Playboys and bragging about back seat virginity triumphs anymore. ...no guy wants to talk to mom about erections and who our first kiss is with.... just be there.....you're already supportive and Atheist. ....I do not know if there is a Boston Women's Collective book for guys but for girls 2 editions exist now OUR BODIES OURSELVES. ....that book would be great to leave next to the microwave, fridge or coffee table where people sit.....curiosity how women talk about themselves lesbian or straight or trans is a mirror for any wise young man. ...imagine how tough it was for me MR MOM for ten years my daughter alone in a political hot house age 6 to 16. ....maybe you could break the ice by asking your son in the parking lot of McDonald's a leading question: " do you know about the pedophile priests raping girls and boys of teen years ?.....a good tangient for him to share his identity perspective without personal mom to son direct gay/straight talk

Just ask "are you gay" because that answer will lead to a ton of acceptance and knowledge.

Is there a problem? Is he unhappy? Does he have friends, doing well in school, and seems to enjoy life (as much as any 16 y/o can)? Let's say he said no...or let's say he said yes to being gay...is there anything in your day to day that would change? I would say if there a change you would make, you are not being an engaged parent to begin with, since really being a good parent is just being involved and letting them know if they need you, you are there. 16 is an age where they need the freedom to grow into adulthood, make mistakes and get hurt. Your job NOW is to ensure the mistakes they make are not so bad as to ruin the rest of their life. It's VERY VERY hard to do, but you have to give them the space to learn. At 18, when life slaps them in the face, they need to have the strength and confidence in themselves from the lessons they learned under your limited guidance to face them as an adult.

I say don't ask, just accept. Don't preach, be kind and loving.
I don't know my 30 year old daughter's sexuality and I don't ask. I know of no males in her life. She lives a few hundred miles away. She has lived with the same female roommate for 9 years? 7?
Honestly, the way the US is headed I would be thrilled if so, her roomie is German and they could escape if need be.

Good advice so far! Don’t assume, don’t push, don’t ask. He’ll let you know when he’s ready. Or he’ll just bring someone home to introduce to you.

Don't just assume that he knows you would accept him - make sure in no uncertain terms that he knows. Parents tend to see themselves as much more open minded than their kids believe them to be.

He may or may not trying to figure this out himself, and "pushing" any teenager, at any time, is Never a good idea unless drugs/death is involved. Plus, many, many quite straight men have effeminate characteristics, so no concluding without his confirmation!
Di you know of any gay people you could casually discuss with him, in an off-hand fashion. (Even from pop culture) And just happen to mention how their parents & friends just want them to be happy? So you are Not talking directly about him?

Just be someone he can talk to. When my daughter was that age, I just let her know that if she got drunk, stoned, pregnant or whatever; that she was still my daughter, and not to be afraid to come to me. She turned into a lovely woman.

Wait for him to tell.
Ever asked a woman when she was due only to be told she wasn't?