“to shitara・to sureba・to suru to”: Supposing 〜 (the three hypothesis-inference siblings) [JLPT N3]

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

“If you were the boss, what would you do?” — the core pattern for inferring from a hypothesis

としたら・とすれば・とすると — three ‘if we suppose ～,' what's the difference?

「宝くじが当たったとしたら／当たったとすれば／当たったとすると、何を買う？」 (if you won the lottery, what would you buy?) — all three say “if we suppose ～, then …,” nearly identical in meaning, which is exactly why they confuse people. This guide sorts out the subtle differences among the three hypothetical-inference forms としたら・とすれば・とすると, separating them from the general conditionals 「たら／ば」 and the concessive 「としても」. (Their practical use and question-word patterns: see 〈とすれば〉.)

Core: suppose a premise, deduce a conclusion (the three forms are synonymous)

「(noun だ／plain clause) ＋ としたら／とすれば／とすると」 = “if we suppose ～, then …” — first positing a premise (not necessarily true), then deducing a logical conclusion:

• この話が本当だとしたら、大変なことだ (if this is true, it's a big deal).
• 明日晴れるとすれば、ハイキングに行こう (if it's sunny tomorrow, let's go hiking).

Feel: “suppose ～, then …” — the core is “supposition ＋ inference”: set a hypothetical premise, deduce “then the conclusion is ….” The three forms are nearly identical in meaning, differing only in subtle feel (below).

Subtle differences (interchangeable, slightly different feel)

Examples in use

• 一億円もらえるとしたら、何に使いますか。(If you could get 100 million yen, what would you use it on?)
• この計画を実行するとすれば、予算が足りない。(If we're to carry out this plan, the budget is short.)
• 全員が参加するとすると、会場を変えなければならない。(If everyone participates, we'll have to change the venue.)
• もし彼が犯人だとしたら、動機は何だろう。(If he's the culprit, what's the motive?)
• 今から出発するとすれば、間に合うだろうか。(If we set off now, will we make it?)

⚠️ Where learners slip up

① The three are interchangeable, but don't mix them with the general conditional 「たら／ば」 — they lean more toward ‘pure supposition ＋ inference.' としたら／とすれば／とすると = suppose a (not necessarily true) premise, deduce a conclusion (本当だとしたら大変だ = if it's true, it's a disaster, with a “supposition” flavor); たら／ば = a general condition (first holds → second holds), more neutral (雨が降ったら中止 = if it rains, cancel). To stress “let's suppose …, then …” inference use the としたら family; for a plain condition use たら／ば.

② 「としたら」 (supposition) ≠ 「としても」 (even if). One character apart, opposite direction. としたら = if we suppose ～ (forward inference: suppose A, then B) (勝ったとしたら、嬉しい = if we won, I'd be happy); としても = even if ～ (concessive reversal: even if A, still B) (勝ったとしても、喜べない = even if we won, I couldn't rejoice). 「たら」 is forward supposition, 「ても」 concessive reversal — don't mismatch. (としても: see 〈としても〉.)

③ The first clause is a ‘supposition,' not an established fact. The としたら family expresses “let's suppose,” the premise not necessarily true, often with 「もし」 (もし〜としたら). If the first clause is an established fact and you mean “though … yet,” that's 「のに」, not としたら. When using it, you're “supposing a situation to infer.”

🔄 Compare: としたら・とすれば・とすると／たら・ば／なら

💡 An exam judgment tip

「としたら・とすれば・とすると」 are the three hypothetical-inference forms, all meaning “if we suppose ～, then …” — set a hypothetical premise, deduce a conclusion. The three are interchangeable in most cases; if forced to split: とすると leans objective natural inevitability (then it works out that…), としたら leans colloquial and particular supposition (if it were …), とすれば leans logical deduction (if so, then…). Two must-remember lines: ① don't reverse it with the concessive 「としても」 — としたら = if A then B (forward inference), としても = even if A still B (concessive reversal); ② the first clause is a ‘supposition' (often with もし), not an established fact. Their practical use and the 「question word ＋ としたら」 (if we're to …) pattern I've written up in 〈とすれば〉 — read both to go deeper. Grasp the core “supposition ＋ inference” and this set is solid.

❓ Common questions

Q: Do としたら, とすれば, とすると really differ? Can I swap them freely?

In most cases yes — all mean “if we suppose ～, then …,” the difference very slight, a matter of “tendency of feel” not “rule”: ① 「とすると」 leans most toward objective, natural inevitable inference — like calculating “then what happens,” with a cool deductive flavor: 全員が来るとすると、椅子が10脚足りない (if everyone comes, we'll be 10 chairs short — objectively computing the result). ② 「としたら」 is most colloquial, often for supposing a particular, concrete case, especially “if it were (someone/some situation)”: もし私があなたとしたら、断ります (if I were you, I'd refuse — supposing a concrete scenario). ③ 「とすれば」 leans most toward logical, reasoned deduction, common in exposition and slightly formal reasoning: この仮説が正しいとすれば、次の結論が導ける (if this hypothesis is correct, the next conclusion follows — logical deduction). But these differences are subtle, and in daily use the three are nearly interchangeable; exams rarely test “which of the three” purely. So the mindset: grasp all three as synonyms (supposition ＋ inference) first, with correct attachment and the right setting (supposition, not established fact); savor the “とすると objective, としたら colloquial, とすれば logical” tendency as advanced feel over time.

Q: 「としたら」 and 「としても」 differ by one character — why so different in meaning?

Because the key is whether it's 「たら (forward supposition)」 or 「ても (concessive reversal)」 — the second half sets the direction. 「〜としたら」 = if we suppose ～, (then) … (forward inference: suppose A holds, deduce B): 優勝したとしたら、みんなで祝おう (if we won the title, let's all celebrate — supposing A, forward to B). It's the forward supposition “if A, then B.” 「〜としても」 = even if ～ (concessive reversal: even if A holds, B is unchanged/still holds): 優勝したとしても、油断はできない (even if we won the title, we can't let our guard down — concession, A holds but the result doesn't follow A). It's the concessive reversal “even if A, still B.” So though both start with 「と＋する」 for supposition, 「〜たら」 leads you forward “suppose → conclusion,” 「〜ても」 leads you backward “even if → nonetheless” — opposite directions. Test: if what follows is “suppose A, (naturally) then B,” use としたら; if “even if A, (still) B,” use としても. (としても's purely-hypothetical concessive use: see 〈としても〉.)

🖊️ Practice Questions (5)

Q1. 「あなたが先生___、どんな授業をしますか？」(If you were a teacher)

(A) だとしたら　(B) だとしても　(C) だとしては　(D) だとしな

Q2. 「彼が6時に出発した___、今頃もう着いているはずだ。」(inference)

(A) としたら / とすれば / とすると (all three OK)　(B) としたらだけ　(C) とすれば だけ　(D) とすると だけ

Q3. What is the most common usage of 「としたら」?

(A) expressing a real condition (something that will definitely happen)

(B) assuming something as a premise to infer or ask

(C) expressing purpose (in order to ~)

(D) expressing a completed action

Q4. 「予算が50万円___、このプロジェクトは無理です。」

(A) だとすれば　(B) だから　(C) なので　(D) だとして

Q5. Which sentence uses 「としたら」most appropriately?

(A) 宝くじが当たったとしたら、旅行に行きたい。(counterfactual assumption)

(B) 明日雨が降ったとしたら、試合は中止です。(a possible condition)

(C) 彼が来ないとしたら、先に始めましょう。(inference)

(D) A, B, C are all correct

Answer Explanations

1. (A) だとしたら ── After a noun (先生), attach だとしたら, hypothesizing the case where you're a teacher.

2. (A) all three OK ── When inferring a result from known information, としたら, とすれば, and とすると can all be used.

3. (B) assuming something as a premise to infer or ask ── The core usage of としたら is a hypothetical premise.

4. (A) だとすれば ── 「予算が50万円だとすれば」, inferring from the budget premise.

5. (D) A, B, C are all correct ── としたら can be used for counterfactual assumptions, possible conditional assumptions, and inference — suitable for all three cases.