Meaning & Usage
Use はずだ to describe an expectation based on objective facts or evidence. While English often uses "should" for both duties and predictions, はずだ focuses purely on logical probability. It communicates: "Based on what I know, it is only natural that X is true."
Think of はずだ as a mental calculation. If Tanaka-san left his house an hour ago and the walk takes ten minutes, he "should" be here now. Logic dictates the outcome. This expression reflects a high degree of confidence—usually 80% to 90%—because it is grounded in a specific reason. The word はず originally referred to the notch of an arrow that fits a bowstring. Just as the notch and string are meant to fit, your conclusion and the situation are meant to align.
Formality levels vary. Use はずだ in casual conversation or private writing. For business or polite settings, switch to はずです. If you want to express a very strong logical denial, use はずがない ("there is no way that...").
Structure & Formation
はず is grammatically a formal noun, so the words preceding it must be in their noun-modifying forms. Note the specific requirements for nouns and な-adjectives below:
| Word Type | Connection Rule | Example |
|---|---|---|
| Verbs | Plain Form (Dictionary/Past/Negative) | 行く + はずだ |
| い-Adjectives | Dictionary Form | 寒い + はずだ |
| な-Adjectives | Add な (na) | 便利 + な + はずだ |
| Nouns | Add の (no) | 日曜日 + の + はずだ |
Don't forget the な or の; these are the most common mistakes for N4 learners. Use the past tense (た-form) if you are expecting something to have already occurred by now.
Example Sentences
1. Expectations Based on Schedules
These examples show how we predict actions based on schedules or habits.
彼はもう駅に着いたはずだ。
kare wa mou eki ni tsuita hazu da.
He should have arrived at the station by now.
天気予報によると、明日は晴れるはずです。
tenki yohou ni yoru to, ashita wa hareru hazu desu.
According to the weather forecast, it should be sunny tomorrow.
田中さんは昨日、風邪をひいたから、今日は来ないはずだ。
tanaka-san wa kinou, kaze wo hiita kara, kyou wa konai hazu da.
Since Tanaka-san caught a cold yesterday, he shouldn't be coming today.
2. Using Adjectives for Predictions
この薬を飲めば、すぐ良くなるはずです。
kono kusuri wo nomeba, sugu yoku naru hazu desu.
If you take this medicine, you should feel better quickly.
このレストランはいつも人が多いから、おいしいはずだ。
kono resutoran wa itsumo hito ga ooi kara, oishii hazu da.
Since this restaurant is always crowded, it should be delicious.
あの映画は有名な俳優が出ているから、面白いはずだ。
ano eiga wa yuumei na haiyuu ga dete iru kara, omoshiroi hazu da.
Since famous actors are in that movie, it should be interesting.
3. Using Nouns and Identifying People
今日は祭日のはずだから、銀行は閉まっている。
kyou wa saijitsu no hazu da kara, ginkou wa shimatte iru.
Today should be a public holiday, so the bank is closed.
彼はアメリカに５年住んでいたから、英語が得意なはずだ。
kare wa amerika ni go-nen sunde ita kara, eigo ga tokui na hazu da.
He lived in America for five years, so he should be good at English.
4. Expressing Discrepancy or Confusion
We often use はずだ when reality contradicts our logic, often accompanied by "but" (ga).
昨日、カバンに入れたはずだが、どこにもない。
kinou, kaban ni ireta hazu da ga, doko ni mo nai.
I'm sure I put it in my bag yesterday, but it's nowhere to be found.
Common Mistakes
Mistake 1: Confusing Logic with Social Duty
❌ 明日は早く起きるはずだ。
✅ 明日は早く起きる**べきだ**。
Use べきだ for things you "should" do as a duty or good idea. Using はずだ about your own future actions makes you sound like a detached observer predicting your own behavior, which is unnatural.
Mistake 2: Missing the "no" with Nouns
❌ 今日は休みはずだ。
✅ 今日は休みのはずだ。
Always connect nouns with の. This is one of the most tested points on the JLPT.
Mistake 3: Missing the "na" with Na-Adjectives
❌ 彼女は親切はずだ。
✅ 彼女は親切なはずだ。
Na-adjectives function like nouns here and require the な connector to be grammatically correct.
Cultural Notes
In Japanese communication, はずだ can serve as a polite way to point out an error. Instead of telling someone "You're late," a speaker might say "The meeting should have started at 2:00" (２時に始まるはずですが). This focuses on the schedule rather than the person, making the criticism feel less confrontational.
You will also hear native speakers muttering はずだ to themselves while searching for lost items. Saying "変だな、あるはずだ..." (Strange, it should be here...) shows the internal struggle when a logical belief fails to match reality.
Related Grammar Points
- Bakari (ばかり) — Just Did, Nothing But (Grammar N4)
- ように (You ni) — So That, In Order To (Grammar N4)
- Sequence and Starting Points: Using てから (te kara) (Grammar N4)
- Substitution & Trade-offs: kawari ni (Grammar N4)
- Using かもしれない (kamoshirenai) to Express Possibility (Grammar N4)
- Using 間に (ma ni) to Describe Actions During a Timeframe (Grammar N4)
JLPT Tips
For the JLPT N4, look for logical clues. If the text provides a reason—like "he lived in Japan for 10 years"—the answer is usually はずだ rather than a simple guess like でしょう.
Pay close attention to the particles in the "Sentence Composition" section. The test often separates の or な from はずだ to see if you know how to connect them. Finally, remember that this grammar is about logic, not desire. You cannot use it to say "I should eat more vegetables"; it only works for "The vegetables should be fresh" (because they were just delivered).