expression
how much; how many; to what extent
Colloquial version of どれだけ, used in casual questions or exclamations about degree or quantity.
See also: どれだけ
どんだけ食べるの？
How much are you going to eat?
どんだけ待てばいいの？
How long do I have to wait?
interjection
oh my god; how ...!; what the ...!; incredible
Interjection expressing surprise, disbelief, or exasperation. Often used as a reaction to something extreme or unexpected.
どんだけ！そんなことありえないよ。
Oh my god! That can't be true.
どんだけすごいんだ、この映画は。
How incredible this movie is!