ないといけないnaito ikenai“must do”

ないといけない means “have to” or “must”. It is the everyday spoken way to talk about obligation in Japanese, and the one you will hear most in real conversation. It is JLPT N5 grammar, and once you know the ない-form of verbs, it takes one step to use.

Literally, ないといけない is "if you don't…, it's no good." Japanese builds "must" out of a double negative.

What does ないといけない mean?

Break the pattern into pieces:

• 行かない — not go
• と — if / when
• いけない — is no good, won’t do

So 行かないといけない is “if I don’t go, it won’t do”, which is simply “I have to go”. You do not need to think about the literal meaning when you speak. But it explains why the verb before と is negative, and why “must” in Japanese looks so long.

English equivalents: have to, must, need to, gotta. In most sentences “have to” is the most natural translation, because ないといけない is conversational rather than stiff.

How to form ないといけない

Take the plain negative (ない-form) of the verb and add といけない. For polite speech, change the end to いけません.

By verb group:

• う-verbs: 行く → 行かないといけない, 待つ → 待たないといけない, 買う → 買わないといけない
• る-verbs: 起きる → 起きないといけない, 食べる → 食べないといけない
• Irregular: する → しないといけない, 来る → 来（こ）ないといけない

Other forms you need:

• Past (“had to”): change only the end. 行かないといけなかった.
• Short casual form: drop いけない completely. もう行かないと。 (I’ve gotta go.)
• Nouns and な-adjectives: use じゃない + と. 静かじゃないといけない (it has to be quiet).

When is ないといけない used?

Personal duties and plans. Things you have to do because of your situation: an early train, homework, a doctor’s appointment. 明日は早く起きないといけない.

Advice to someone close. With よ at the end, it becomes friendly advice: 薬を飲まないといけないよ (You need to take your medicine, you know).

Leaving. The cut-off form ないと is the classic way to excuse yourself: そろそろ帰らないと (I should get going).

Simple rules. 図書館では静かにしないといけません (You have to be quiet in the library). Written rules and formal texts prefer なければならない, but in speech ないといけない is normal for rules too.

Register: ないといけない is plain and friendly. ないといけません is polite enough for teachers and coworkers. The short ないと is casual.

ないといけない example sentences

Note 薬を飲む in the fifth sentence: Japanese “drinks” medicine, so 飲む is the right verb even for pills.

Nuance of ないといけない

It feels personal. ないといけない often carries the speaker’s own sense of “I really should”. It suits reasons you feel in the moment: a deadline, a promise, your health. That is why it is so common in daily speech.

It is softer than it looks. In English, “you must” can sound harsh. Japanese ないといけない with よ or ね sounds like caring advice, not an order. For a direct instruction, Japanese uses てください instead.

It is not a prohibition. いけない alone means “no good”. てはいけない means “must not”. Only when a negative verb comes before と does the meaning become “must”. Keep the ない in front and you are safe.

💡 Family of forms: ないといけない, なければいけない, なくてはいけない and the casual なくちゃ all mean "have to". At N5 you mainly need to recognise them. For speaking, ないといけない and ないと cover almost every situation.

ないといけない vs なければならない

Both mean “must”. The difference is mostly register and feel.

If you are talking to a person, ないといけない is almost always the natural choice. If you are writing a set of rules or reading a textbook, expect なければならない. The full N4 lesson is at なければならない.

Common mistakes with ないといけない

Is ないといけない on the JLPT?

Listening questions often ask “What does the woman have to do next?” The answer is usually in a ないといけない or ないと sentence, so train your ear to catch the verb right before と.

Practice questions for ないといけない

Learning path for ないといけない

Related grammar to review next

• なくてはいけない — same meaning, built with なくては instead of ないと, a little more textbook in tone
• なくちゃ — the casual contraction you hear alongside ないと in fast speech
• なくてもいい — “don’t have to”, the answer when an obligation does not apply
• てはいけない — “must not”, which uses the same いけない but a positive て-form
• なければならない — the formal, written version of the same obligation

Learn ないといけない with Hane

Hane trains the ない-form and the obligation patterns built on it, so 行かないといけない and 来なくてもいい come out right when you need them. Practice with Hane.