아/어야 돼요: How Korean Says Have To and Must
아/어야 돼요 (or 아/어야 해요) is how Korean says have to, must, or need to. Attach 아야 or 어야 to a verb stem by vowel harmony, then add 되다 or 하다 in the 요-form — 가야 돼요 means "I have to go," 먹어야 해요 means "I have to eat." Both endings mean the same thing; 돼요 just sounds a shade more spoken, 해요 a shade more formal.
Every grammar book presents 아/어야 되다 and 아/어야 하다 as two separate patterns to memorize, complete with a chart explaining their subtle differences. This is the single most overengineered explanation in beginner Korean. They mean the same thing. You'll hear both in the same conversation, sometimes from the same person, thirty seconds apart.
What actually matters is the piece nobody drills enough: how to attach the ending correctly, and — this is the part that trips people up for months — how to say the opposite of "have to," because Korean does not build it the way English does.
Building 아/어야 돼요 from a verb stem
Strip the 다 off any verb, check the last vowel, then pick 아야 or 어야: bright vowels (ㅏ, ㅗ) take 아야, everything else takes 어야. Tack on 되다 or 하다 in the 요-form and you're done.
가야 돼요.
ga-ya dwae-yo
I have to go.
가다 → 가 + 아야 → contracts to 가야
해야 해요.
hae-ya hae-yo
I have to do it.
하다 → irregular 하여야 → contracts to 해야
먹어야 돼요.
meo-geo-ya dwae-yo
I have to eat.
먹다 → 먹 + 어야, dark vowel stem
와야 돼요.
wa-ya dwae-yo
You have to come.
오다 → 오 + 아야 → contracts to 와야
돼요 vs 해요: stop agonizing
Here's the opinion part: pick one and move on. 아/어야 되다 leans slightly more spoken — it's what you'll hear in dialogue, in DMs, in a friend texting you "나 지금 가야 돼" mid-conversation. 아/어야 하다 leans slightly more written or formal — announcements, instructions, a manager laying out policy. But the gap is small enough that Koreans cross it constantly without noticing. Nobody has ever been side-eyed for saying 먹어야 해요 instead of 먹어야 돼요.
| Context | Natural choice | Why |
|---|---|---|
| Texting a friend | 가야 돼 | 돼요-family reads as spoken, casual |
| Store hours sign | 예약을 해야 합니다 | 하다-family reads as formal, written |
| Casual conversation, either works | 먹어야 돼요 / 먹어야 해요 | genuinely interchangeable here |
If you're not sure which one to reach for, reach for 돼요. It covers more ground in daily speech and it's what you'll hear most in Korean drama dialogue.
The drama exit line: 나 가야 돼
If you've watched more than three K-dramas, you've heard this line delivered while someone is already halfway out a door: 나 가야 돼 ("I have to go"), banmal, clipped, no explanation offered. It's the standard way a character exits a scene they don't want to be in — a phone buzzes, they glance at it, they stand up. Adding 요 (나 가야 돼요) makes it polite without changing the drama of it.
옥상 가서 얘기 좀 하자.
ok-sang ga-seo yae-gi jom ha-ja.
Let's go up to the roof and talk.
미안, 나 가야 돼.
mi-an, na ga-ya dwae.
Sorry, I have to go.
또? 요즘 계속 이러네.
tto? yo-jeum gye-sok i-reo-ne.
Again? You keep doing this lately.
스케줄 있어서 가야 할 것 같아.
seu-ke-jul i-sseo-seo ga-ya hal geot ga-ta.
I have a schedule, so I think I need to go.
That softened version, 아/어야 할 것 같아요, is worth learning right alongside the plain form. Stack 것 같아요 onto 아/어야 하다 and "I have to go" turns into "I think I probably should go" — the version you use with your boss, not your bandmate.
"Don't have to" is not the opposite of "have to" — the trap
English learners instinctively try to negate 가야 돼요 by sticking 안 in front of it: 안 가야 돼요. Don't. It's not standard Korean, and native speakers will pause on it. Korean builds "don't have to" and "must not" as two completely separate patterns, and mixing them up flips your meaning entirely.
| Meaning | Pattern | Example |
|---|---|---|
| Have to / must | 아/어야 되다·하다 | 가야 돼요 — I have to go |
| Don't have to (optional) | 안 + 아/어도 되다 | 안 가도 돼요 — I don't have to go |
| Must not (forbidden) | (으)면 안 되다 | 가면 안 돼요 — you must not go |
The pattern to internalize: 아/어도 돼요 always signals optional ("it's fine either way"), and (으)면 안 돼요 always signals forbidden. 아/어야 돼요 sits by itself as required. Three patterns, three different jobs — Korean just doesn't let you build the negative of "required" by slapping 안 on the front of it the way English does with "don't have to."
Frequently asked questions
What's the difference between 아/어야 돼요 and 아/어야 해요?
Nothing meaningful. Both express obligation. 아/어야 되다 leans slightly more spoken and casual, 아/어야 하다 leans slightly more formal or written, but Koreans swap between them constantly in the same conversation. Learn one, understand both.
How do I say "don't have to" in Korean?
Use 안 + verb stem + 아/어도 돼요, not a negated version of 아/어야 돼요. 안 가도 돼요 means "you don't have to go." 안 먹어도 돼요 means "you don't have to eat." This is a different grammar pattern from "have to," not its negation.
Is 나 가야 돼 rude to say?
It's banmal (casual speech), fine among friends, family, or people younger than you — but not to a boss or stranger. Add 요 for a polite version: 저 가야 돼요. Same meaning, appropriate register for anyone you're not close with.
Is it 돼 or 되 — which spelling is correct?
돼 is a contraction of 되어; use it wherever "되어" would fit if you spelled it out, including at the end of a sentence (가야 돼). 되 alone attaches to something else, like 되고 or 됩니다. Even native speakers mix these up constantly — you're in good company.
What's the difference between 가야 돼요 and 가야 할 것 같아요?
가야 돼요 states the obligation directly: "I have to go." Adding 것 같아요 ("seems like/I think") softens it into a hedge: "I think I should go." Same underlying obligation, gentler delivery — useful when you want to leave a conversation without sounding abrupt.