The Difference Between〜はず (hazu) vs 〜べき (beki)｜Japanese Grammar (N5–N3)

(Joy calculating time [Hazu] vs. Joy enforcing rules [Beki])

“He should be at home now.” (Logic)
“You should be kind to others.” (Morals)
In English, “Should” covers both. In Japanese, 〜はず (Hazu) is for logic/expectation, and 〜べき (Beki) is for duty. Mixing these up can make you sound very bossy! Let’s learn with Joy and Ken.

🗣 Conversation Scene

Joy and Ken are waiting for Tanaka-san, who is late.

Joy

田中さん、遅いですね。
「すぐ行く」と言っていたので、もう着（つ）くはずです。
(Tanaka-san is late. He said “I’m coming now,” so he “should/is expected to” arrive soon.)

Ken

困りましたね。時間は守（まも）るべきですよね。
(That’s troubling. One “should/must” keep track of time, right?)

💡 Explanation

Is it a Calculation or a Rule?

Point 1: 〜Hazu (〜はず) = Expectation / Logic

Meaning: “It is supposed to…” / “I expect that…”
Based on facts, evidence, or schedules, you calculate a result. It is objective.

彼は日本に10年住んでいたから、日本語ができるはずだ。
(He lived in Japan for 10 years, so [logically] he should be able to speak Japanese.)
このボタンを押（お）せば、動（うご）くはずです。
(If you press this button, it is supposed to move.)

Point 2: ~Beki (〜べき) = Duty / Moral

Meaning: “Must” / “Ought to” / “It is the rule”
Based on common sense, morals, or laws. It judges whether something is “Good or Bad.”

約束（やくそく）は守るべきだ。
(You must keep promises. [Moral rule])
もっと勉強（べんきょう）するべきだった。
(I should have studied more. [Regret/Reflection])

📊 Comparison Table

Phrase	Focus	English Nuance
〜はず (Hazu)	Logic / Fact / Schedule	“Supposed to” “I expect that”
〜べき (Beki)	Morals / Obligations	“Must” “Moral duty”

🚧 Joy’s Mistake

(Joy is waiting for the train, but it hasn’t come.)

❌ Wrong: 電車（でんしゃ）は 来るべき です！
(Translation: “It is the train’s moral duty to come!” This sounds weird. You are treating the train like a human with morals.)

✅ Right: 電車は 来るはず です！
(Translation: “According to the schedule, it is supposed to be here.” This is a logical expectation.)