How much / how many / to what extent — used to ask about amount, degree, or extent.
どれだけ時間がかかりますか？
How long will it take?
彼がどれだけ努力したか、みんな知らない。
Not everyone knows how much effort he put in.
どれだけお金が必要か、見積もってみよう。
Let's estimate how much money is needed.