I don’t know about you but I’ve always wondered whether it is “Where are you? or “Where are you at?” and “Where are you going?” or “Where are you going to?”
David Crystal illustrates the use in the context of X who is on the train, travelling to meet Y, and Y wants to check up on whether he’ll be there in time. Y calls his mobile and asks ‘Where are you?’ X replies ‘I’m on the train’. Y is not really happy with X’s reply and insists ‘Yes but where are you?’. He has to reconsider and goes ‘Yes, but where are you at?’
To cut it short:
Y: Where are you?
X: I’m on the train.
Y: Yes, but where are you at?
X: I’ve reached Sportcity.
David Crystal says that particles help to sharpen the focus of the question. It makes perfect sense to me that it’s not really about the location when we use such end-placed particles but rather on the person’s state of mind or stage of achievement.
How do you use them?