目錄
Japanese 「〜はずだ」 expresses an objective, affirmative inference the speaker makes based on the clues available to them. In Chinese, it is often translated as “should” or “ought to.” What tends to be genuinely confusing, however, is not its literal meaning but its subtle sense of time. When 「〜はずだ」 places a judgment in the present or future and then changes into the past form 「〜はずだった」, the expectation that originally seemed valid is shifted back into the past, creating a sense that something fell through or that the speaker later realized things had not gone as expected.
What Does the Japanese 「はずだ」 Mean? Why Is It More Than Just “Should”?
The key to 「〜はずだ」 is that it expresses an inference based on evidence, not simply a wish or a subjective expectation. The speaker usually has some basis for the judgment, such as a timetable, common knowledge, context, or known information, and therefore concludes that something should logically be true. For example, if a train timetable says the train arrives at ten, you can say 「もう着いているはずだ」. This is not a guarantee; it is a reasonable conclusion reached after considering the information currently available.
Japanese 「はずだ」 and 「はずだった」: Conjugation and Grammar Rules
「〜はずだ／〜はずだった」 Attachment Rules
| Type | Pattern | Example | Meaning |
| Verb plain form | V plain form＋はずだ | 来るはずだ | Infer from the situation that someone will come |
| い-adjective | い-adjective＋はずだ | 高いはずだ | It should be expensive |
| な-adjective | な-adjective＋な＋はずだ | 静かなはずだ | It should be quiet |
| Noun | Noun＋の＋はずだ | 休みのはずだ | It should be a day off |
| Past expectation | Plain form＋はずだった | 来るはずだった | It was originally expected to happen, but the result may have differed |
「〜はずだ」 Usage ①｜Making a Present Inference Based on Clues
This usage often appears when the speaker already has some objective clue, such as a timetable, a prior agreement, a weather forecast, or a store notice. The focus is on the idea that “based on the information currently available, the situation should be like this.” It is more evidence-based than 「と思う」 and expresses greater confidence than 「かもしれない」.
- Example: 田中さんはもう会社に着いているはずだ
Kana: たなかさんはもうかいしゃについているはずだ
Translation: Mr. Tanaka should already have arrived at the office.
The speaker may know his commuting time or when he left home, so they make a reasonable inference about his current state. - Example: この店は今日は開いているはずだ
Kana: このみせはきょうはあいているはずだ
Translation: This shop should be open today.
The judgment is based on its business days or an announcement, rather than being a casual guess. - Example: 資料は机の上にあるはずだ
Kana: しりょうはつくえのうえにあるはずだ
Translation: The documents should be on the desk.
The speaker infers their current location based on where they were last placed.
「〜はずだ」 Usage ②｜Expressing That a Future Event Should Happen According to Plan
When the sentence refers to the future, 「〜はずだ」 often carries the sense of “this should happen according to the plan.” It is neither a command nor a personal wish; instead, it uses an existing plan, system, or arrangement as the basis for the inference. It is commonly used when talking about travel, meetings, flights, and exam announcements.
- Example: 電車は十時に到着するはずだ
Kana: でんしゃはじゅうじにとうちゃくするはずだ
Translation: The train should arrive at ten.
The future event is inferred from the timetable, with the scheduled time serving as the basis. - Example: 明日には結果が出るはずだ
Kana: あしたにはけっかがでるはずだ
Translation: The results should be out by tomorrow.
This is judged from an announcement or process and does not mean the speaker can control the result. - Example: 予約してあるから、席は取れているはずだ
Kana: よやくしてあるから、せきはとれているはずだ
Translation: Since we made a reservation, the seats should be secured.
The first half provides the basis for the inference, while the second half presents the affirmative judgment.
「〜はずだった」 Usage ③｜Expressing That Something Was Supposed to Happen but Did Not Go as Expected
「〜はずだった」 places an inference or expectation in the past and often implies that the actual result did not match what had been expected. In Chinese, it can be translated as “was originally supposed to,” and it often carries a sense of surprise, regret, or looking back after the fact. This is the biggest difference in time perspective between 「〜はずだ」 and 「〜はずだった」.
- Example: 彼は会議に来るはずだった
Kana: かれはかいぎにくるはずだった
Translation: He was supposed to come to the meeting.
In reality, he may not have shown up, so the sentence suggests that the expectation was not fulfilled. - Example: 昨日届くはずだった荷物がまだ来ない
Kana: きのうとどくはずだったにもつがまだこない
Translation: The package that was supposed to arrive yesterday still hasn’t come.
「昨日」 and 「まだ来ない」 make the sense of the failed expectation especially clear. - Example: ここは静かなはずだったのに、工事の音がする
Kana: ここはしずかなはずだったのに、こうじのおとがする
Translation: This place was supposed to be quiet, but I can hear construction noise.
「のに」 makes the contrast between expectation and reality even clearer.
What Is the Difference Between 「はずだ」 and 「はずだった」? Comparing Their Sense of Time
| Comparison | 「〜はずだ」 | 「〜はずだった」 |
| Time of judgment | Present or future | Past expectation |
| Core nuance | Based on the clues, it should logically be so | It was originally expected to be so, but often differs from reality |
| Common Chinese translation | 應該、理應 | 原本應該 |
| Emotional tone | Neutral, affirmative | Regret, surprise, disappointment |
| Commonly used with | もう、今日、明日、予約してある | 昨日、去年、のに、まだ |
▌「〜はずだ」 Looks at Present or Future Clues
✅ Natural: 予約してあるから、席は取れているはずだ
This sentence uses “the reservation has already been made” as the basis for the inference that the seats should be secured. The focus is on the information currently available, not on a failed expectation viewed afterward.
▌「〜はずだった」 Looks Back at an Earlier Expectation
✅ Natural: 昨日届くはずだった荷物がまだ来ない
「はずだった」 places the expectation in the past, and 「まだ来ない」 then shows that reality has not caught up with that expectation. This sense of discrepancy is something 「はずだ」 cannot replace.
Japanese 「はずだ」 in Real Travel Conversations: Checking Transportation and Accommodation When Reality Differs from Expectations
When traveling, 「〜はずだ」 is often used to confirm transportation, hotel reservations, opening hours, and whether people have arrived at a meeting point. It does not guarantee anything; it expresses a reasonable inference based on a booking, timetable, or announcement. If the actual situation differs from the original arrangement, 「〜はずだった」 can express the gap implied by “it was supposed to be this way.”
▌Situation ①｜Checking Whether a Friend Has Arrived at the Station
A：田中さんはもう駅に着いているはずだよ
たなかさんはもうえきについているはずだよ
Mr. Tanaka should already have arrived at the station.
B：じゃあ、改札の前を見てみよう
じゃあ、かいさつのまえをみてみよう
Then let’s check in front of the ticket gates.
📌 Grammar Point: Combining 「もう」 with 「着いているはずだ」 expresses an inference about the current state based on time.
▌Situation ②｜The Hotel Room Is Different from What Was Expected
A：この部屋は海が見えるはずだった
このへやはうみがみえるはずだった
This room was supposed to have an ocean view.
B：予約内容をもう一度確認したほうがいいね
よやくないようをもういちどかくにんしたほうがいいね
We should probably check the reservation details again.
📌 Grammar Point: 「はずだった」 indicates that the expectation beforehand differs from the situation now, giving a strong sense that things did not go as expected.
Cultural Notes:
- In Japanese service settings, reservations, timetables, and announcements are treated as important reference points, so 「〜はずだ」 often appears together with information that can be checked.
- 「〜はずだった」 is also very useful while traveling. It can be used for room types, seats, delivery times, and itinerary arrangements whenever the actual result differs from what was expected.
- When confirming something with a clerk or front-desk staff member, using 「〜はずですが」 is softer than making a direct assertion and better matches the interpersonal distance commonly maintained in Japanese communication.
How Does Japanese 「〜はずだ」 Compare with Korean 「-(으)ㄹ 것이다」?
◆ Similar Grammar: Korean 「-(으)ㄹ 것이다」
Korean 「-(으)ㄹ 것이다」 can express either a prediction or a future plan, and like Japanese 「〜はずだ」, it can incorporate the speaker’s judgment into the sentence. However, the Korean form has a broader range of uses: it may simply function as a future form, or it may express a prediction. Japanese 「〜はずだ」 places stronger emphasis on the idea that “there is evidence, so logically this should be the case.”
- Example: 기차는 곧 도착할 것이다
Romanization: gi-cha-neun got do-chak-hal geo-si-da
Translation: The train should arrive soon.
This sentence can express a future prediction and is close in nuance to the Japanese 「電車はもうすぐ着くはずだ」. - Example: 예약했으니 자리는 있을 것이다
Romanization: ye-yak-haet-seu-ni ja-ri-neun i-sseul geo-si-da
Translation: Since we made a reservation, there should be seats.
The first half provides the basis for the inference, making the nuance close to 「予約したから席はあるはずだ」. - Example: 계획대로라면 이미 끝났을 것이다
Romanization: gye-hoek-dae-ro-ra-myeon i-mi kkeut-na-sseul geo-si-da
Translation: If everything went according to plan, it should already be finished.
「계획대로라면」 provides the basis for the inference, making the nuance close to the Japanese 「予定通りなら、もう終わっているはずだ」.
◆ Core Difference from 「〜はずだ」:
「〜はずだ」 usually has a clear basis for the inference and often carries the nuance of “logically, this should be the case.” Korean 「-(으)ㄹ 것이다」 can also simply express the future, so the strength of the inference has to be determined from context. To express a failed expectation, Japanese uses 「〜はずだった」, while Korean often uses forms such as 「-기로 되어 있었다」 or 「-았/었어야 했다」.
The core value of Japanese 「〜はずだ」 cannot really be understood by forcing it into the two Chinese characters 「應該」 alone. At its heart, the speaker looks at the available clues and concludes, “Given this, it should logically be true.” Once the timeline is pushed back into the past and the form becomes 「〜はずだった」, the tone naturally shifts from rational, objective inference to the surprise, disappointment, or resignation that comes with an expectation not being fulfilled. When you encounter clues such as 「のに」, 「まだ」, or 「予約した」 in Japanese sentences, try following the timeline and noticing whether the speaker is inferring the current situation or talking about a plan that fell through.
FAQs
「〜はずだ」 expresses an affirmative inference based on objective clues and is often close to the Chinese 「理應」 or 「應該」. It is usually not based on mere feeling, but on information such as timing, common knowledge, announcements, agreements, or context. When clues such as 「もう」, 「予約してある」, or 「予定では」 appear in the sentence, the inferential nuance becomes even clearer.
「〜はずだ」 has a more objective basis than 「と思う」. 「と思う」 can simply express a personal opinion, while 「〜はずだ」 usually suggests that the speaker has some reason for the judgment. For example, 「来ると思う」 means “I think they’ll come,” while 「来るはずだ」 means that based on an agreement, procedure, or common sense, they logically should come.
「〜はずだった」 very often indicates that an expectation was not fulfilled, but whether the event actually failed to happen still depends on context. If it is followed by expressions such as 「のに」, 「まだ」, or 「実際は」, the sense of disappointment or discrepancy is usually strong. If it simply looks back on a past plan, it may only mean “that was what was originally scheduled at the time” without directly stating the outcome.
「〜はずだ」 itself can be used in formal or semi-formal contexts, but formal writing may use 「〜はずです」 or replace it with a more objective expression. In everyday conversation, both 「はずだ」 and 「はずです」 are natural. In business contexts, however, care is needed so that an inference does not sound like an absolute guarantee.
You can think of 「〜はずだ」 as “making an inference now based on available clues,” and 「〜はずだった」 as “looking back on what was originally expected in the past.” The former looks toward the present or future, while the latter looks back on something that either happened or failed to happen. When reading a sentence, first identify the time adverb, then check whether expressions such as 「のに」 or 「まだ」 appear afterward; this usually makes the nuance easier to identify.