～なければならない / ～なきゃいけない (nakereba naranai / nakya ikenai) – must do

Ever need to say “I have to go” or “You must study” in Japanese? That’s where「～なければならない」and its more casual cousin「～なきゃいけない」come in.

Both mean “must do” or “have to”.

Let’s break it down 👇

What Does ～なければならないMean?

「～なければならない」is the formal, polite way to say:

“must / have to / need to”

Think of it as saying: “If I don't do it, it would be bad.”

Example:

べんきょうしなければなりません。

Benkyou shinakereba narimasen.

→ I must study.

You’ll hear this version in:

Work situations
School settings
News and formal speech

But in casual daily life, people usually say…

～なきゃいけない(More Common & Casual)

This is the spoken, shortened form of ～なければならない.

Example:

もうかえらなきゃいけない。

Mou kaeranakya ikenai.

→ I gotta go home.

Same meaning, but more natural for talking with friends.

You might also hear:

～なきゃ→ ultra casual version (dropping theいけない)
- たべなきゃ！(Gotta eat!)
- トイレに行かなきゃ！(Gotta go to the bathroom! )
～なくちゃ(another variant with same meaning)
- 急がなくちゃ！(Gotta hurry!)

How to Conjugate Verbs to ～なければ/ ～なきゃ

Here’s how to turn a verb into this “must” form:

1. Start with the ない-form of the verb (negative form)

2. Removeない

3. Add:

なければならない（formal）
なきゃいけない（casual）
なきゃ（super casual）

Examples:

たべる → たべない→たべなければならない/たべなきゃいけない
いく → いかない→いかなければならない/いかなきゃいけない
する → しない→しなければならない/しなきゃ
くる → こない→こなければならない/こなきゃ

⚠️ Note:するandくるare irregular, so memorize theirない-forms.

Examples

Here are sentences you'll probably hear in Japan:

あしたははやくおきなきゃ。 → I gotta wake up early tomorrow.
しゅくだいをやらなきゃいけない。 → I have to do my homework.
パスポートをもっていかなければなりません。 → You must bring your passport.
このくすりをのまなきゃ。 → I have to take this medicine.
あやまらなきゃ。 → I have to apologize. 🥲

Try It Yourself!

How would you say...

I have to leave.
I have to study Japanese.
I have to clean my room.
I gotta sleep soon.

Answers:

でなきゃいけない。/でなければなりません。
日本語をべんきょうしなきゃ。
へやをそうじしなきゃ。
もうねなきゃ。

Cultural Note: Obligation, Indirectly

Japanese people often soften expressions of obligation. Even if it’s a “must,” they might say it in a lighter tone, especially when asking someone else. You can use the 〜ほうがいい grammar instead if you're suggesting someone do something.

Instead of saying:

あなたはやらなければなりません！ "You must do it!" ❌ (Unless you're one of those super strict teachers...)

They might say:

やったほうがいいと思います。→ “I think it’s better if you do it.” ✅
やらなきゃだめかな〜？ → “I guess I have to do it…” (softer, indirect)

This helps keep the conversation more harmonious and avoids sounding too bossy. Japanese culture cares a lot about keeping relationships harmonious, so try not to demand too much of others with this grammar form.