ないといけない

The structure ないといけない expresses obligation or necessity – that something must be done. It literally means "if (one) doesn't do (something), it won't do," which conveys the idea of "must" or "have to."

It is formed by attaching と + いけない to the negative form of a verb:

• いく行く → 行かない → 行かないといけない (must go)
• たべる食べる → 食べない → 食べないといけない (must eat)
• する → しない → しないといけない (must do)

Basic usage

Use ないといけない when expressing that something is required or necessary.

The polite form uses いけません instead of いけない.

Casual shortened forms

In casual speech, ないといけない is often shortened to ないと by dropping いけない, since the meaning is understood from context.

An even more casual contraction is なきゃ (from なければ):

Related forms

ないといけない is one of several ways to express "must" in Japanese:

• なければならない – more formal and often used in writing
• なくてはいけない – similar meaning, uses なくては instead of ないと
• ないといけない – natural in everyday conversation

All of these express the same core meaning, but ないといけない is among the most common in spoken Japanese.