文法Grammar Point
koto ni suru · JLPT N4
〜ことにする means “decide to”. It is a JLPT N4 pattern: below are its construction, the nuances that trip learners up, and the sentences where real Japanese writers use it.
A free one-page study card for 〜ことにする (decide to), JLPT N4: what it means, how it attaches, 3 example sentences with furigana, and the nuances that trip learners up. Read it right here, or take the PDF or PNG with you. We never ask for an email for this card.
毎朝走ることにしました is “I’ve decided to run every morning.” Attach it to the dictionary form, or to the ない-form to decide against something. Its near-twin 〜ことになる reports a decision that was made for you or that simply came about — telling those two apart is most of what learning this pattern involves, because Japanese often prefers the passive-sounding one even when you did the deciding.
構文Construction
Verb (dictionary form) + ことにする
来年、留学することにしました。 — I’ve decided to study abroad next year.
Verb (ない-form) + ことにする — deciding against
甘い物は食べないことにしました。 — I’ve decided not to eat sweets.
〜ことにしている — a rule you have set for yourself
毎日日記を書くことにしています。 — I make a point of writing a diary every day.
Compare 〜ことになる — decided by circumstances
来月、大阪に転勤することになりました。 — It’s been decided that I’ll transfer to Osaka.
例文In a sentence
来年、日本に留学することにしました。
今日からお酒を飲まないことにします。
毎朝六時に起きることにしています。
注意点Nuances
練習Your Turn
Each one is quoted from a published Japanese text in this library and links to the story it came from. Some use older spellings, or break off where the sentence carried on. They are transcribed exactly as their authors wrote them.
蟹は、じぶんの子どもたちをみなとこやにしました。
— from The Crab's Barber Business (N4)
僕は小学教員をかせいで、そのかせぎためた金で、上京して苦学をしようと思い立ったものだ。
— from The Hundred-Faced Actor (N1)
腹一杯喰っておくことにしよう。
— from The Embassy's Cleanup Agency (N1)
彼女は女給になろうと思う。
— from The Waitress (N1)
Appears in 6 of 367 texts in our library.
蔵書The texts
Free to read in full. Furigana over every kanji, a dictionary on any word you tap, and an English breakdown of each sentence.
解説Background
〜ことにする sits at JLPT N4 in the 302-point taxonomy every text in this library is tagged against. Each text is read for the patterns it contains, which is what lets this page list every text that uses 〜ことにする and pull its example sentences out of them.
The example sentences were not written to demonstrate the rule. They are quoted from published Japanese texts in this library (The Crab's Barber Business and The Hundred-Faced Actor among them), and each one links back to the story it came from, so you can read the sentence where it actually happened.
質問Questions
ことにする is your own decision; ことになる is a decision that was reached for you or by circumstances. 会社を辞めることにしました says you chose to quit. 会社を辞めることになりました suggests the situation left you no choice — or is simply a modest way of announcing it.
It marks a rule you have set yourself and continue to follow: 夜はコーヒーを飲まないことにしています (“I make a point of not drinking coffee at night”). The plain 〜ています would only report the habit, without the decision behind it.
Use the ない-form before ことにする: 行かないことにしました (“I’ve decided not to go”). Do not negate する itself — ことにしませんでした means you never made the decision at all.
Yes. A free one-page 〜ことにする (decide to) study card sits at the top of this page, as both a PDF and a PNG. It carries the JLPT N4 meaning, how the pattern attaches, 3 example sentences with furigana, and the nuances learners get wrong. You do not need an account or an email address to download it.
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