How big of an age gap is needed to be considered weird for dating for 21 year olds?

[Cerebrate]

If she's still in high school and you're in college/university, I'd say that's a bit skeezy.

This. It's only naturally to be attracted to high school girls, but I don't think you should date one or anything.

[Yau]

At 23, the thought of dating anyone under 21 is not ideal to me.

[OneSent]

You can't put a number on relationships. There is no math. There is no formula.

Whether she is 17 or 18, if you find her interesting enough and attractive, then there's nothing holding you back from pursuing the chance at a relationship with her; nothing, but the taboos of our society.