～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.