How do you say "where is the bathroom" and "i need to ise the bathroom"

Question

Answer

where is the bathroom? : 화장실 어디있나요?
i need to use the bathroom : 화장실 가고싶어요(화장실에 가야해요)
so if you need to use the bathroom, you can say "where is the bathroom(or  toilet)?"

Answer

Where is the bathroom is:
화장실 어디있어?
Or
(저는) 화장실 어디있어요?
I need to use the bathroom is:
저는 화장실에 갈 필요가 있어요./ 저는 화장실에 갈 필요해요.
Or
나는 화장실 갈 필요해
Depending on how respectful you want to be

Answer

욕실이 어디예요? (Where is the bathroom?)
욕실 쓰고 싶어요/화장실 써야 해요. (I need to use the bathroom.)

욕실 means bathroom, but Korean houses nornally contain a loo in the bathroom, so you can say 화장실 instead. But when you mean only BATH not LOO, then you have to use 욕실.

Answer

Where is the bathroom = 화장실이 어딘가요? [hwa jang sil i eo din ga yo?]
I need to use the bathroom = 화장실에 가야해요. [hwa jang sil e ga ya hae yo.]

Bathroom = 화장실 [hwa jang sil]