Japanese grammar

What does ～はずだ mean? Japanese grammar N3

～はずだ means should be ~; ought to be ~; bound to ~ (based on expectations/evidence).

Quick facts
Level (estimated, JLPT framework)	N3
Structure	普通形 + はずだ Aな + な + はずだ Nの + はずだ
Romaji	hazuda
Meaning	should be ~; ought to be ~; bound to ~ (based on expectations/evidence)

Forming it

Noun	休み + の + はずだ
Verb	届く + はずだ
na-adjective	元気な + はずだ

How to use it

States a well-grounded assumption that something is true or will happen as a matter of course; the speaker is fairly confident but not stating it as an absolute certainty.

「～はずだ」 states a WELL-GROUNDED assumption based on reasoning or known information: "by rights, it should…".
Also used upon realizing "ah, no wonder" — when what was guessed turns out to be correct.
Different from 「～わけだ」: 「はずだ」 is an expectation/assumption made beforehand; 「わけだ」 is a natural conclusion drawn after learning something.

Examples

手紙(てがみ)は明日(あした)届(とど)くはずです。
The letter should arrive tomorrow.
彼(かれ)はこの道(みち)をよく知(し)っているはずだ。
He should know this road well.

Keep in mind

Nouns connect with 「の」, な-adjectives connect with 「な」.
The negative 「～ないはずだ」 (surely not) differs from 「～はずがない」 (no way).

Common mistakes

Wrong彼(かれ)は先生(せんせい)だはずだ。

He must be a teacher.

Correct彼(かれ)は先生(せんせい)のはずだ。

A noun connects to 「はずだ」 with 「の」 (先生のはずだ).
Wrongたぶん来(く)るはずがない。

He'll probably not come.

Correctたぶん来(こ)ないはずだ。

"Probably won't come" uses 「～ないはずだ」; 「はずがない」 means "no way" (stronger).

Exam tips

「はずだ」 = a well-grounded assumption; the negative 「ないはずだ」 (probably not) ≠ 「はずがない」 (no way).