“〜to sureba・to shitara・to suru to”: Supposing 〜, If 〜 (hypothesis then inference) [JLPT N3]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

“If you were to fail, what would you do?” — supposing a situation, then inferring or advising

「一つだけ選ぶとすれば、どれ？」 — suppose first, then deduce the natural conclusion

「もし一つだけ選ぶとすれば、どれにしますか」 (if you had to pick just one, which would it be?) — 「〜とすれば」 (also としたら・とすると) is used to posit a premise first, then deduce the natural conclusion or evaluation. This guide focuses on its practical use: how to build “supposition → conclusion” reasoning with it, and the very handy 「question word ＋ とすれば／としたら」 (if we're to …, then … ?) pattern. (The subtle differences among とすれば/としたら/とすると: see 〈としたら〉.)

Core: posit a premise, deduce the ‘naturally so' conclusion or evaluation

「(plain clause) ＋ とすれば／としたら」 = “if we suppose ～, then (naturally) …” — set a supposition, then deduce the conclusion, evaluation, or question that naturally follows under it:

• この情報が正しいとすれば、事態は深刻だ (if this information is correct, the situation is serious).
• 彼の言う通りだとしたら、私たちは騙されていたことになる (if it's just as he says, then we've been deceived).

Feel: “if ～, then (naturally) …” — the point is deducing the ‘inevitable, natural' next step under a supposed premise. The second clause is often an evaluation (大変だ・問題だ), a judgment (〜ことになる), or a question (どうする？).

Attachment & the ‘question word ＋ とすれば' pattern

Examples in use

• もし一人だけ推薦するとしたら、彼女を選びます。(If I could recommend just one, I'd choose her.) — question-word premise
• この数字が正しいとすれば、来月は赤字だ。(If these figures are correct, next month is in the red.) — supposition → conclusion
• 今から始めるとすると、終わるのは深夜になる。(If we start now, we'll finish late at night.) — natural computation
• 生まれ変われるとしたら、何になりたい？ (If you could be reborn, what would you want to be?) — question-word premise
• 全部本当だとすれば、これは大事件だ。(If it's all true, this is a huge incident.) — supposition → evaluation

⚠️ Where learners slip up

① Very handy: 「question word ＋ としたら／とすれば」 = if we're to …, then … ? To ask “if we're to (make some choice), what/where/who would we pick,” question word ＋ verb ＋ としたら／とすれば is most natural: 一つ買うとしたら、どれ？ (if we're to buy one, which?); 留学するとすれば、どの国？ (if we're to study abroad, which country?); 誰かに頼むとしたら、誰にする？ (if we're to ask someone, who?). It's a common “hypothetical question” frame in conversation and interviews — worth memorizing.

② 「とすれば」 (hypothetical inference) ≠ 「からすれば」 (judging from a standpoint/basis). They look alike, different functions. とすれば = if we suppose ～ (positing a premise) (本当だとすれば = if it's true); からすれば = from ～'s view／judging by ～ (evaluating from a standpoint or basis) (親からすれば、心配だ = from a parent's view, it's worrying; この証拠からすれば、彼は無実だ = judging by this evidence, he's innocent). 「とすれば」 supposes, 「からすれば」 is “from the standpoint of…／based on…” — don't confuse them.

③ Don't fret over the three forms' subtle differences — grasp ‘supposition → conclusion' first. とすれば／としたら／とすると are nearly interchangeable here (the difference is slight; see 〈としたら〉). In use, what matters isn't which form, but whether you build a sound ‘supposed premise → natural conclusion': whatever you suppose in front, deduce the result that naturally follows under it. Connecting the reasoning matters far more than agonizing over the three forms.

🔄 Compare: とすれば／たら／なら／からすれば

💡 Quick takeaway

This guide teaches you to use 「とすれば・としたら・とすると」 well: the core move is “posit a premise first, then deduce the conclusion, evaluation, or question that naturally follows under it” (正しいとすれば深刻だ; 本当だとしたら騙されていた). The most practical trick is 「question word ＋ verb ＋ としたら／とすれば」 = if we're to …, then … ? (一つ選ぶとしたら、どれ？; 留学するとすれば、どの国？) — great for hypothetical questions in conversation and interviews. Two reminders: ① don't confuse it with 「からすれば」 (judging from a standpoint/basis) — とすれば supposes, からすれば is standpoint/basis; ② don't fret over the three forms' subtle differences (to split them, see 〈としたら〉) — in use, soundly connecting “supposition → natural conclusion” matters most. Master supposing-and-questioning and deducing conclusions, and your Japanese gains a handy thinking frame.

❓ Common questions

Q: How exactly do I use 「question word ＋ としたら／とすれば」 (e.g., どこへ行くとしたら)?

It's a very practical variant of the hypothetical-inference pattern: first use 「verb ＋ としたら／とすれば」 to suppose ‘we're to make some choice/action,' then use a question word to ask ‘which/where/who specifically.' The structure is “(もし) ＋ question word ＋ verb ＋ としたら／とすれば、〜？.” Examples for feel:

• 旅行に行くとしたら、どこへ行きたい？ (if we're to travel, where would you want to go?) — suppose “we travel,” ask “where.”
• 一つだけ買えるとすれば、何を買う？ (if we could buy only one, what would you buy?) — suppose “only one,” ask “what.”
• 誰かをリーダーに選ぶとしたら、誰がいい？ (if we're to pick a leader, who?) — suppose “pick a leader,” ask “who.”

The benefit of this frame: wrapping the question in a “supposition” makes it less direct, easier to answer (since it's just “if”), so it's common in interviews and chat (e.g., 「もし生まれ変われるとしたら、何になりたいですか」). Remember the formula: (もし) ＋ the choice to make (verb) ＋ としたら／とすれば ＋ question word 〜？, and you can naturally pose all kinds of “if we're to …, then … ?” hypothetical questions.

Q: 「とすれば」 and 「からすれば」 differ slightly — same meaning?

Wholly different — don't mix them just because they look alike. 「〜とすれば」 = if we suppose ～ (positing a premise, then inferring): この報告が正しいとすれば、計画を見直すべきだ (if this report is correct, we should review the plan — “report correct” is a supposition, deducing “should review”). What precedes is a supposed condition. 「〜からすれば」 = from ～'s view／judging by ～ (evaluating from a standpoint, or based on some fact), with two common uses: ① from a standpoint — 子供からすれば、親の心配はうるさい (from a child's view, parents' worry is annoying); ② judging by a fact — あの態度からすれば、彼は怒っているようだ (judging by that attitude, he seems angry). What precedes is a standpoint or a basis for judgment, not a supposition. Trick: what precedes is ‘a supposed situation' → とすれば (if …); what precedes is ‘a standpoint or basis' → からすれば (from …／based on …). E.g., 「専門家だとすれば」 = if he's an expert (supposing he is); 「専門家からすれば」 = from an expert's view (he is one, taking that standpoint). One supposes, one is standpoint/basis — very different.

🖊️ Practice Questions (5)

Q1. 「もし宝くじが当たった___、何に使う?」(if you won the lottery, what would you use it for)

(A) としたら　(B) とたん　(C) うちに　(D) ところ

Q2. 「この情報が正しい___、計画を変える必要がある。」(if this information is correct, you need to change the plan)

(A) とすれば　(B) からこそ　(C) わりに　(D) どころか

Q3. 「彼が犯人だとすると、つじつまが合う」の意味は?

(A) If he is the culprit, (reasoning it through) it makes sense

(B) He is definitely not the culprit

(C) He must be the culprit

(D) Nothing to do with the culprit

Q4. 「としたら／とすれば」の語感として正しいのは?

(A) Assume a situation holds and reason onward from it

(B) Happens only after an action is completed

(C) Takes what the other person said as the premise

(D) Indicates contrast

Q5. 接続が正しいのは?

(A) 本当だとすれば大変だ。　(B) 本当とすればだ大変。

(C) 本当をとすれば大変。　(D) 本当だとすればの大変。

Answer Explanations

1. (A) としたら ── If you won the lottery (hypothetical reasoning).

2. (A) とすれば ── If the information is correct, you need to change the plan.

3. (A) ── If he is the culprit, the reasoning makes sense.

4. (A) ── Assume it holds and reason onward.

5. (A) ── Plain form ＋ とすれば; the other connections are wrong.