How to Say "I Don't Know" in Korean (Without Sounding Rude)

"I don't know" in Korean is 몰라 (molla) in casual speech, or the polite 몰라요 (mollayo). But most Koreans actually say 모르겠어요 (moreugesseoyo) — the same verb softened with -겠, which turns a flat "I don't know" into "I'm not sure," and sounds far less like a shrug in someone's face.

Here's the trap: English has one "I don't know," and its tone depends entirely on delivery — flat, apologetic, exasperated, whatever you make it. Korean built the tone into the grammar. Say the wrong version to the wrong person and you've gone from "I'm honestly unsure" to "not my problem," without changing a single word of meaning.

The verb is 모르다 (moreuda, to not know — Korean doesn't have a separate "don't know," it has a whole verb that means not-knowing). What changes is how you dress it.

몰라, 몰라요, 모르겠어(요): the four forms

That -겠 is doing real work. It's the ending Korean uses for guesses and inferences (you'll also see it in 알겠습니다, "understood"), and slotting it into 모르다 quietly reframes the sentence from a statement about reality — "I do not possess this knowledge" — into a statement about your own uncertainty — "I'm not sure I can say." It's the linguistic equivalent of softening "no" into "I don't think so." Nothing else in the sentence changes. Just that one syllable, and the whole thing stops sounding like a wall going up.

The shrug package: 글쎄요 and 아마

Koreans rarely answer a hard question with a bare "I don't know" at all — they hedge first. Two words do most of that work, and neither one is technically "I don't know," which is exactly why they're useful.

글쎄요 in particular is a Korean-conversation MVP. It doesn't commit to knowing or not knowing — it just stalls, gracefully, while you figure out what you actually think. English speakers reach for "um" or "I mean"; Korean has a whole word built for exactly that pause.

몰라! as a drama pout

This is the usage that trips up every learner watching with subtitles: someone shouts 몰라! and the subtitle says "I don't know!" — but nobody just asked them a question. That's because 몰라! stopped being about information a long time ago. Shouted, clipped, usually followed by turning away, it means something closer to "I don't want to deal with this" or "I'm done talking to you." It's a pout, not an answer.

You'll hear the same shout from a kid refusing to explain why they're crying, or a couple mid-argument. Context is everything: if there's no actual question on the table, 몰라! isn't information, it's mood.

잘 모르겠어요: your best beginner escape hatch

If you only remember one phrase from this article, make it 잘 모르겠어요 (jal moreugesseoyo) — "I'm not really sure." It's polite, it's honest, and it gets you out of almost any situation where a question in rapid Korean has left you completely lost, whether that's a teacher calling on you or a clerk asking something you half-caught.

This is also the phrase to reach for when someone asks something you do understand but can't answer in Korean yet. "잘 모르겠어요" buys you room to switch to English, point at your phone, or just take a breath — nobody reads it as you giving up on the conversation.

The rude one: when 몰라요 lands wrong

Here's my one hard opinion on this topic: textbooks teach 몰라요 as the default polite "I don't know" and it's a small trap. Yes, -요 makes it grammatically polite. But say bare 몰라요 to a shopkeeper, a stranger, or your boss and it can land closer to "not my problem" than "I'm unsure" — because it skips the -겠 hedge that actually signals humility. The politeness marker is there; the softening isn't.

This is the same logic behind 은/는 vs 이/가 or 반말 vs 존댓말: Korean politeness isn't one switch, it's several, and this is a case where missing the second one matters more than getting the first one right.