How do I know if he's gay? Girls AND GUYS help!?

I’m best friends with a guy? We’ve been best friends all the way through high school. So I know him pretty well. He’s always been completely normal in every way. He’s never ever shown any signs whatsoever of being gay. He’s had girlfriends, dresses like a regular high school dude would and talks about girls just like a normal honry teenage guy would at 18. But recently when we were talking, we somehow got onto the subject of how girls can look at another girl and be like “Wow, she’s really hot” and not be gay for saying that. He said that he can do the same thing, and tell if a guy is hot or not. I didnt really think that was weird or anything, because us girls do that to. But then he asked me if when I look at a girl that I think is hot, if I get a “tingly” feeling? I didnt know what he meant, because I’ve never had that happen to me, but he said it happens to him. Soo, does that mean he’s gay or is this a normal guy thing?