-기로 하다: Decide / Agree To

-기로 하다 is how Korean marks a decision that has been made — "decide to / agree to / resolve to." Where -(으)려고 하다 reports an intention that is still just an intention, and -(으)ㄹ 거예요 states a plan or a prediction, -기로 하다 reports a plan that has crossed the line into a settled commitment — often one arrived at jointly, after talking it over. That single fact explains its most surprising feature to English speakers: even though the decided action lies in the future, the sentence almost always ends in the past tense, 했어요, because it is the deciding that has already happened.

The shape

-기로 하다 is built from the nominalizer -기 (turning the verb into "the doing of X"), the particle -로 ("as/toward"), and 하다 ("do"): literally "make it as [doing X]." It attaches to a verb stem with no allomorphy at all — no 받침 split, no vowel harmony. Just add -기로 하다:

To decide not to do something, negate the verb: 안 …기로 하다 or …지 않기로 하다.

The core meaning: a concluded decision

The prototypical -기로 하다 sentence is a personal resolution — the moment you settle on a course of action. This is the Korean of New Year's resolutions, of "that's it, I'm quitting," of firm choices.

That last example shows a key flexibility: the 하다 slot can be filled by a more specific verb of deciding. Swap in 결심하다 (resolve), 결정하다 (decide), 약속하다 (promise), or 정하다 (settle on) to name the exact act.

The reframing: why the future action takes the past tense

Here is the thing that feels backwards to English speakers. In "우리 내일 만나기로 했어요," the meeting is tomorrow — clearly future — yet the sentence ends in 했어요 (past). English forces "we've decided to meet tomorrow," splitting the past decision from the future meeting into two verbs. Korean packs both into one clause and lets 하다 carry the tense: the deciding is what already happened, so 하다 goes past, while the verb before -기로 stays a bare stem naming the still-future action.

Once you see 했어요 as "the decision is now a fact," this stops looking odd and starts looking precise. A present-tense 하기로 해요 is also possible, but it lands differently — it proposes or arranges a rule going forward rather than reporting a done deal, so it often works as a soft mutual suggestion:

It naturally covers "we agreed to," not just "I resolved to"

English "decide" leans individual, so learners forget that -기로 하다 is the default way to report a mutual agreement. Because a joint decision is exactly a decision that has been concluded between people, -기로 하다 owns this territory. Any arrangement two or more people have settled — a meeting time, a shared trip, a group rule — is -기로 했어요.

-기로 하다 vs. -(으)려고 하다: concluded vs. still-forming

This is the contrast worth drilling, because it is the commonest meaning-level error. Both point at a future action, but the commitment level is different:

• -(으)려고 하다 = an intention that is still just an intention — "I'm thinking of / planning to." Nothing is locked; you could change your mind and no one would be let down.
• -기로 하다 = a decision that is concluded — "I've decided / we've agreed." The matter is settled, often with someone else counting on it.

For a wedding date the two of you have fixed, you say 결혼하기로 했어요 — not 결혼하려고 해요, which would reduce a firm commitment to a mere musing. If someone can be disappointed when you back out, you are in -기로 하다 territory.

-기로 하다 vs. -(으)ㄹ 거예요: the decision vs. the plan or prediction

-(으)ㄹ 거예요 states a plan (first person) or a prediction (third person), but it says nothing about a decision process. -기로 하다 specifically foregrounds that a choice was made — which is why it shines when the deciding itself is the news.

Say 그 회사에 안 갈 거예요 and you flatly report a plan ("I'm not going to join"); say 안 가기로 했어요 and you report the verdict of a deliberation ("I've come down against it"). The extra "I weighed it and settled it" is the whole value of -기로 하다.

Common Mistakes

1. Using -(으)려고 하다 for a settled or agreed plan. Intention isn't decision.

2. Putting the future action in the past instead of 하다. The verb before -기로 stays a bare stem; only 하다 carries tense.

3. Attaching it to an adjective. A decision is to do something; you can't decide "to be tall." -기로 하다 takes action verbs.

4. Forgetting it covers group agreements. For "we decided / we agreed," 우리 …기로 했어요 is the go-to; learners often over-explain with 같이 동의했어요 when -기로 했어요 already says it.

Key Takeaways

• -기로 하다 marks a concluded decision or mutual agreement — "decide to / agree to / resolve to."
• It attaches to verb stems with no allomorphy; negate the verb (안 …기로 / …지 않기로).
• The future action normally sits in the past (했어요) because the deciding is what happened; present 해요 proposes/arranges going forward.
• 하다 can specialize to 결심하다 / 결정하다 / 약속하다 / 정하다.
• Contrast -(으)려고 하다 (still-forming intention) and -(으)ㄹ 거예요 (plan/prediction) — -기로 하다 is the one that says the matter is settled.