〜ことにする
Formation
Meaning
Used when saying that you have decided to do or not do something of your own volition.
Note
Indicates a personal decision, choice, or a deliberate habit that the speaker has committed to. It emphasizes the speaker's own will or intention ('I have decided'). The variant '〜こととする' is more formal and is often used in official documents or formal speeches to announce a decision. Contrast this with '〜ことになる', which describes a decision made by others or external circumstances.
Examples
健康のために、毎日走ることにしました。
I've decided to run every day for my health.
あまりお腹が空いていないので、お昼は食べないことにします。
I'm not very hungry, so I've decided not to eat lunch.
今年の夏休みはどこにも行かないことにした。
I've decided not to go anywhere this summer vacation.
明日からはもっと早く起きることにする。
I'll make it a point to wake up earlier starting tomorrow.
今後、この規則を適用することとする.
It is hereby decided that this rule shall be applied hereafter.