Practice JLPTHow to tell them apart
はず expresses a confident expectation based on evidence or logic — you believe something is or was the case, like 高かったはずだ (I expect it was expensive). べきだ expresses a moral or logical judgment that something ought to be done or be the case, like あるべき所 (where it should be). The key distinction is that はず describes what you think is true, while べきだ describes what you think is right or desirable. Swapping them is unnatural: saying 高かったべきだ sounds wrong because it mixes expectation with obligation, and あるはずの所 changes a normative claim into a mere guess.
- はず Use はず when you are fairly confident something is or was true based on evidence.
- べきだ Use べきだ when expressing a judgment that something ought to be done or be so.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| はず hazu | Expectation / should be | N4 |
| べきだ bekida | Should/Ought to | N3 |
はず hazu
Expectation / should be
I expect that ~; it is expected that ~; ~ is expected to; I am fairly certain that ~; should; ought to; it is natural that ~; no wonder ~ | A dependant noun which expresses the speaker’s expectation that something will take place or took place or that someone/something is or was in some state.
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あの本は高かったはずだ。
I expect that book was expensive.
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そのアパートは奇麗なはずです。
I expect that apartment is clean.
べきだ bekida
Should/Ought to
Should; ought to | An auxiliary which expresses the speaker's judgment that someone/something should do something or should be in some state.
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あるべき所に 記述がない。
There's no description where there should be one.
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この状態が現実であるべきだ。
This state should be the reality.
はず and べきだ are JLPT N4–N3 grammar points that Japanese learners often mix up. This page compares them side by side — meanings, usage and example sentences — so you can tell them apart.