Grammar › Obligation › 〜なくてもいい
〜なくてもいい
The relief valve: "you don't have to / it's fine not to." One も flips must into no need.
The short version
Take the verb's negative (行かない), swap the final い for くてもいい: 行かなくてもいい = "you don't have to go" — literally "even not doing it is fine". Swap いい for 大丈夫 and you get the same "it's OK not to".
行く → 行かなくてもいい — don't have to go
行かなくても大丈夫 — it's OK not to go
〜なくてもいい — no need to
Reassuring someone that an action isn't required.
食べなくていいですよ。
You don't have to eat it. (食べない → 食べなくていい)
何もしなくてもいいんですね。
You don't have to do anything at all. (しない → しなくてもいい)
〜なくても大丈夫 — "it's OK not to"
大丈夫 ("all right / fine") swaps in for いい with a warmer, reassuring tone.
心配しなくても大丈夫です。
You don't have to worry. (心配しない → 心配しなくても大丈夫)
Watch out
One も is all that separates "must" from "no need". 〜なくてはいけない = "must"; 〜なくてもいい = "don't have to". Slip the も in and the obligation disappears.
🗣 The も usually drops: なくていい. In casual speech people say 行かなくていい, 食べなくていい — same meaning, one syllable lighter. You'll also hear なくて大丈夫 without も.
Next: 〜ほうがいい — had better → · 〜ないで → · All grammar
Free on Wakatta — learn Japanese by listening. Every example above is a real line from a Japanese podcast, timestamped so you can hear it.