に決まっている details
of course it is; is bound to be — the speaker treats it as beyond argument
そんな話、嘘に決まってるじゃない。
sonna hanashi, uso ni kimatteru ja nai.
A story like that has got to be a lie. casual
今から走っても、終電には間に合わないに決まっている。
ima kara hashitte mo, shuuden ni wa ma ni awanai ni kimatte iru.
Even if we run now, there's no way we'll make the last train. neutral
- contraction
- past
- polite
Examples
of course it is; is bound to be — a conclusion the speaker treats as too obvious to argue about
そんな話、嘘に決まってるじゃない。
sonna hanashi, uso ni kimatteru ja nai.
A story like that has got to be a lie. casual
今から走っても、終電には間に合わないに決まっている。
ima kara hashitte mo, shuuden ni wa ma ni awanai ni kimatte iru.
Even if we run now, there's no way we'll make the last train. neutral
一人でこの量を運ぶのは無理に決まっています。
hitori de kono ryou o hakobu no wa muri ni kimatte imasu.
Carrying this much alone is obviously impossible. neutral
Formation
plain clause + に決まっている（N・na-adjはそのまま接続 — 無理に決まっている）attaches to plain clause{N}にきまっているattaches to noun
Variant notes
- に決まってる — the everyday spoken shape — い drops from ている, as it does everywhere else: そんなの嘘に決まってるよ.
Notes
listener's disagreement, so it stays out of formal writing and out of
anything said to a superior.
Related patterns
Similar
に違いない lays its evidence out and can be answered with counter-evidence; に決まっている puts none of its grounds up for inspection — it presents the conclusion as needing no argument and treats disagreement as unreasonable, which is why it lands in spoken retorts (嘘に決まってるでしょ) and not in a written report.
はずだ points at a schedule, rule or known fact the listener can check (三時に着くはずだ), and survives being wrong (はずだったのに, the timetable's fault); に決まっている has no such retreat — taking it back means conceding the speaker was being unreasonable, not that the facts misled them.
Two ends of one register scale at near-identical certainty — に相違ない commits the conviction to a document where it must withstand scrutiny, に決まっている says it out loud and refuses to be argued with; neither survives being moved into the other's setting.
Opposite
- わけがないplain-antonym
The spoken pair a learner reaches for in the same breath — に決まっている asserts it must be so and わけがない that it cannot be, both refusing argument out loud; に違いない／はずがない are the same two poles in the register that will still write them down.
Lookalikes
決まる's literal "be decided" is the trap — 会議は三時に決まっている reports a fixed arrangement, exactly what ことになっている does, while the pattern reading is the speaker's own verdict on what something is (犯人はあいつに決まっている) and reports nobody's decision at all.