-(으)ㄴ/는/(으)ㄹ 것 같다 vs -나 보다, -(으)ㄴ가 보다

Intermediate · TOPIK II

-(으)ㄴ/는/(으)ㄹ 것 같다 is a general guess and also a soft way of giving your opinion (even about your own feelings); -나 보다/-(으)ㄴ가 보다 is an inference from evidence you observe, and isn't used for your own direct experience.

-(으)ㄴ/는/(으)ㄹ 것 같다An expression used to indicate that the statement is a guess.-나 보다, -(으)ㄴ가 보다An expression used to guess about a fact mentioned in the preceding statement.

Rules of thumb

Inferring from visible clues (people have umbrellas → it's raining): -나 보다 is very natural.
Softening your own opinion or feeling (이 옷은 좀 작은 것 같아요 'This seems a bit small'): only -것 같다.
Don't use -나 보다 for what you directly experienced (you tasted it and it's spicy → 매운 것 같아요, not 매운가 봐요).
Guesses about the future: -(으)ㄹ 것 같다 (비가 올 것 같아요); -나 보다 is rarely used for the future.
Forms: verb + -나 보다, adjective + -(으)ㄴ가 보다, past -았/었나 보다.

Example sentences

-나 보다, -(으)ㄴ가 보다
People are using umbrellas. It must be raining outside.
-(으)ㄴ/는/(으)ㄹ 것 같다
I think this is a bit small for me.
-(으)ㄴ/는/(으)ㄹ 것 같다
The sky is cloudy. It looks like it'll rain soon.
(직접 먹어 보고) 이 떡볶이는 정말 매운가 봐요.
Incorrect
(After tasting it) This tteokbokki seems really spicy. [Wrong: for your own direct experience, use -(eu)n geot gatda, not -na boda]
-나 보다, -(으)ㄴ가 보다
Minsu keeps yawning. He must not have slept last night.

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