Practice JLPTHow to tell them apart
The core contrast is volition: ことにする marks a decision the speaker or group makes themselves, while ことになる marks a decision made by circumstance, an outside party, or an arrangement already in place. Swapping them sounds odd — saying 来月引っ越すことにした means you chose to move, whereas 来月引っ越すことになった means it was decided for you or things just turned out that way.
- ことになる Use ことになる when a plan or outcome is decided by someone else or by circumstance, not by you.
- ことにする Use ことにする when you or your group actively make a decision to do something.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| ことになる kotoninaru | It is decided that / turn out | N4 |
| ことにする kotonisuru | Decide to | N4 |
ことになる kotoninaru
It is decided that / turn out
It will be decided that ~; come about ~; be arranged that ~; turn out that ~ | An event takes place as if spontaneously, irrespective of the speaker's volition.
-
スミスさんは日本で英語を教えることになっている。
It has been decided that Mr. Smith will teach English in Japan.
-
今日山田先生に会うことになっています。
Today (it's been arranged that) I'm seeing Professor Yamada.
ことにする kotonisuru
Decide to
Decide to | A volitional decision to do something is made.
-
京都までバスで行くことにしましょう。
Let's (lit. decide to) go as far as Kyoto by bus.
-
今年の夏は北海道を旅行することにしました。
I've decided to make a trip to Hokkaido this summer.
ことになる and ことにする are both JLPT N4 grammar points that Japanese learners often mix up. This page compares them side by side — meanings, usage and example sentences — so you can tell them apart.