〜ことになる: 'It's Been Decided That…' (Meaning + Examples)
What it means
〜ことになる tells your listener that a decision has been reached and you're simply reporting the outcome. The grammar puts the focus on the result rather than on who chose it, so it sounds as if the decision came from outside you — from your company, your family, or just how things worked out. Even when you arranged something yourself, Japanese speakers often use this pattern to sound modest and avoid taking credit. You can usually translate it as "it has been decided that…" or "it turns out that…".
ヤッタンは来月、大阪に転勤することになった。
ヤッタンは らいげつ、おおさかに てんきんする ことになった。
It's been decided that Yattan will transfer to Osaka next month.
The company decided — Yattan just reports it.
モチと一緒に日本へ留学することになりました。
モチと いっしょに にほんへ りゅうがくする ことに なりました。
It's been decided that I'll study abroad in Japan with Mochi.
その店は来週、閉まることになった。
そのみせは らいしゅう、しまる ことに なった。
It turns out that store will close next week.
How to form it
Attach ことになる to the plain (dictionary) form of a verb. For the negative meaning ("it's been decided we won't…"), use the plain ない-form:
| Verb form | + ことになる | Example |
|---|---|---|
| Dictionary form | 行く → 行くことになる | 行くことになった = it's been decided we'll go |
| ない-form | 行かない → 行かないことになる | 行かないことになった = it's been decided we won't go |
| Past result | 〜ことになった | 結婚することになった = it's been decided we'll marry |
| Standing rule | 〜ことになっている | 出すことになっている = you're supposed to submit it |
The verb なる here keeps its core meaning of "becoming" — a situation becomes settled. You'll most often see it in the past tense (ことになった), because you're reporting a decision that has already been made.
A decision that feels external
The whole point of this pattern is that the decision sounds like it came from somewhere other than your own will. Compare these in plain English:
- 来年、結婚することになりました。 — "It's been decided we'll marry next year." (Sounds modest, as if arranged or settled by circumstances.)
- 来年、結婚することにしました。 — "I've decided we'll marry next year." (A clear personal decision.)
That second pattern, 〜ことにする, is the choice you make yourself — it has its own guide. Throughout this article we'll keep using ことになる for the "settled by others/circumstances" meaning.
話し合った結果、弟が犬の世話をすることになった。
はなしあった けっか、おとうとが いぬの せわを する ことになった。
After discussing it, it was decided that the little brother would look after the dog.
A group decision, not one person's call.
先生のおかげで、スピーチ大会に出ることになりました。
せんせいの おかげで、スピーチたいかいに でる ことに なりました。
Thanks to the teacher, it's been decided I'll take part in the speech contest.
〜ことになっている — rules, schedules, and customs
Change なる to its て-いる form and you get 〜ことになっている, which describes a rule, custom, or arrangement that is currently in force. Think "the rule is that…" or "you're supposed to…". The decision was made at some point in the past and still stands now.
この学校では日本語を話すことになっている。
このがっこうでは にほんごを はなす ことに なっている。
At this school, you're supposed to speak Japanese.
A standing school rule.
ヤッタンは毎朝、モチと公園を走ることになっている。
ヤッタンは まいあさ、モチと こうえんを はしる ことに なっている。
Yattan is supposed to run in the park with Mochi every morning.
A fixed routine or arrangement.
図書館では飲み物を飲まないことになっています。
としょかんでは のみものを のまない ことに なっています。
In the library, you're not supposed to drink beverages.
This is the form to reach for when you explain office rules, school policies, or "the way things are done here."
Common mistakes
- Using the ます-form before ことになる. Attach it to the plain form: 行くことになった (✓), not 行きますことになった (✗).
- Confusing it with the decision you made yourself. ことになる = settled by circumstances/others; for your own choice use the separate pattern 〜ことにする.
- Forgetting なっている for rules. A standing rule is 〜ことになっている (ongoing). 〜ことになった alone reports a one-time decision, not a continuing rule.
- Dropping ない for negatives. "It's been decided we won't go" is 行かないことになった, not 行かないことにした (that last one is your own choice).
Quick recap
- 〜ことになる = it has been decided / it turns out — the decision feels external or modest.
- Attach it to the plain verb (dictionary or ない-form); it's usually past: ことになった.
- 〜ことになっている = a standing rule, schedule, or custom ("you're supposed to…").
- For a decision you personally make, use the separate 〜ことにする pattern instead.
Your turn
Choose the correct form of 〜ことになる / 〜ことになっている.
Start the 5-question drill →Take the full N4 〜ことになる drill →
Frequently asked questions
What's the difference between ことになる and ことにする?
ことになる reports a decision made by circumstances or other people (転勤することになった = it's been decided I'll transfer). ことにする is a decision you make yourself (転勤することにした = I've decided to transfer). Same situation, different responsibility.
Why use ことになる if I actually made the decision myself?
It sounds modest. By phrasing your own arrangement as something that 'was decided,' you avoid drawing attention to yourself — a very natural, polite move in Japanese, common for news like marriage or moving.
What does ことになっている mean?
It describes a rule, schedule, or custom that is still in effect: 9時に始まることになっている ('it's set to start at 9'). Use it for office rules, school policies, and routines — 'you're supposed to…'.
Which verb form comes before ことになる?
The plain form: dictionary form for positive (行くことになる) and the ない-form for negative (行かないことになる). Never use the ます-form here.