To summarize, use -(으)ㄹ게요 when:1. changing plans according to what the other person said;2. checking or assuming what the other person thinks by saying something using this ending and seeing his/her reaction;3. deciding to do something because of what the other person said.

Sample Sentences

지금 어디예요? 지금 나갈게요.[ji-geum eo-di-ye-yo? ji-geum na-gal-kke-yo.]= Where are you now? I will go out now.(+ if you do not mind / if you want me to / unless you do not want me to / what do you think about that?)

• You cannot use “지금 나갈 거예요” [ji-geum na-gal kkeo-ye-yo] here because it means that you were already going out anyway, and more than likely to an unrelated place, regardless of where the other person is located.

저 갈게요. 안녕히 계세요.[jeo gal-kke-yo. an-nyeong-hi gye-se-yo.]= I am going to go. Take care.(+ unless you want me to stay longer / unless there is something I have to stay longer to do)

• You cannot use “저 갈 거예요” [jeo gal kkeo-ye-yo] because it is implying that you do not care whether or not the other person wants you to stay because you are leaving anyway. You would only say it when you do not want the other person to ask you to stay because you have absolutely no intention of staying even if you are asked.

그래요? 다시 할게요.[geu-rae-yo? da-si hal-kke-yo.]= Is that so? I will do it again.

• If you say “다시 할 거예요” [da-si hal kkeo-ye-yo] here instead of “다시 할게요” [da-si hal-kke-yo] implies that you were already aware of the problem and you were going to do it again anyway. This comes off as a little insulting.

내일 4시쯤에 갈게요. 괜찮아요?[nae-il ne-si-jjeu-me gal-kke-yo. gwaen-cha-na-yo?]= I will be there at around 4 o’clock tomorrow. Is that alright?

• By saying “내일 4시쯤에 갈 거예요” [nae-il ne-si-jjeu-me gal-kkeo-ye-yo] here instead, you are implying that you do not care what the other person thinks nor do you care if going at 4 o’clock will affect the other person’s schedule; therefore, you do not care if it is okay or not, which makes you sound rude.