Which floor or what floor?

[salt&pepper]

"Which floor" or "what floor"

For example if you're in the elevator, there a person coming in and you would like to help him/her to press the level button.
How do you ask?

"Hello, which floor are you going?"
OR
"Hello, what floor are you going?"

 

[SoothingDave]

"Which" is more correct, but "what" is commonly used.

I would say "Which floor are you going to?" if forced to use a whole sentence.

Simply "Which floor?" would normally suffice.