N1 Emotion and Feeling

~だろうに: meaning, usage and examples

~だろうに means: ...I'm sure / ...must be (expressing sympathy, regret).

Updated 9 November 2026 · By the My Senpai team · Spotted a mistake? Tell us

Examples

1. 彼かれは疲つかれているだろうに、文句一もんくひとつ言いわずに手伝てつだってくれた。

   He must have been tired, but he helped me without a single complaint.

2. あそこで諦あきらめなければ、優勝ゆうしょうできたろうに。

   If only he hadn't given up there, he could have won.

3. もう少すこし早はやく家いえを出でていれば、間まに合あっただろうに。

   If I had left home a little earlier, I would have made it in time.

4. 電車でんしゃで行いけば早はやいだろうに、父ちちはいつも車くるまで行いきたがる。

   Taking the train would surely be faster, but my father always wants to drive.

When to use it

Two uses. Mid-sentence it means "even though surely ...": 疲つかれているだろうに手伝てつだってくれた. At the end, with a condition, it expresses regret about what could have been: 相談そうだんしてくれれば力ちからになれただろうに, I could have helped if you had asked. Example: 早はやいだろうに, it would surely be faster, yet...

Nuance

Conversation and writing; sympathy, regret or mild criticism. The ending use often follows ば or たら and leaves the regret unsaid. The speaker is guessing, so it is not used for facts the speaker knows for sure.

Compare

のに states a fact with frustration: 雨あめなのに出でかけた. だろうに adds a guess: 寒さむいだろうに出でかけた (surely it was cold, but they went). ものを is the literary regret form: 言いえばいいものを. ただろうに is the common past regret.

Tip: Break it down: だろうに = だろう (guess) + のに (frustration). If you know the fact for certain, use plain のに instead.