how much / how many; asks about degree or amount
その本はどれほどの値段でしたか？
How much did that book cost?
会議はどれほど長く続きますか。
How long will the meeting last?
どれほどの人数が来るかまだ分からない。
I still don't know how many people will come.
no matter how (much); however (used in constructions like どれほど…ても/でも)
どれほど練習しても、まだ不安だ。
No matter how much I practice, I'm still anxious.
どれほど説明しても彼には伝わらないようだ。
However much I explain, it doesn't seem to get through to him.
どれほど努力しても結果が出ないこともある。
No matter how hard you try, sometimes you don't get results.
(with negation) hardly; barely; not much
彼はどれほども勉強していないようだ。
He hardly seems to have studied at all.
その仕事にどれほどの時間もかからなかった。
That job barely took any time.