The short answer
All four translate as “if”, but they carry different logic. たら is the safe default: “if/when X happens, then Y”, and it works with any kind of main clause. ば puts the spotlight on the condition itself (“only if X”). と describes a result that follows automatically, every time. なら picks up something that is true or has just been said and gives advice or a reaction about it: “if that’s the case”.
| たら | ば | と | なら | |
|---|---|---|---|---|
| Meaning | if / when / after X happens | if (the condition is met) | whenever X, Y follows | if it’s the case that X |
| Typical use | one-off events, requests, plans | conditions, advice (〜ばいい) | natural laws, habits, directions | reacting to a topic, advice |
| Request or intention in the second half? | yes | limited | no | yes |
| Example | 着いたら電話して。 | 安ければ買う。 | 押すと開く。 | 行くなら予約して。 |
たら in a nutshell
たら means “if” or “when”, and it always implies that the first event is completed before the second one happens. Take the plain past form and add ら: 行った → 行ったら, 高かった → 高かったら, 雨だった → 雨だったら.
Because it has the fewest restrictions, たら is what you use in conversation when you are not sure which conditional fits. It is also the only one of the four that can mean “when (certainly) X happens”, with no doubt about whether X happens at all.
駅に着いたら、電話してください。
Call me when you get to the station.
もし宝くじが当たったら、世界一周したい。
If I won the lottery, I'd want to travel around the world.
家に帰ったら、荷物が届いていた。
When I got home, a package had arrived.
ば in a nutshell
ば is the textbook “if”. It focuses on what must be true for the result to happen, so it often sounds like “as long as” or “only if”. For verbs, change the final -u sound to -e and add ば: 行く → 行けば, 食べる → 食べれば, する → すれば. い-adjectives take ければ (安い → 安ければ); nouns and な-adjectives take であれば (or なら).
The catch: when the ば clause is an action and both clauses share a subject, the second half cannot be a request, invitation or intention. If the ば clause is a state (an adjective, ある, いる, a potential verb), that restriction disappears.
毎日練習すれば、上手になりますよ。
If you practice every day, you'll get good at it.
安ければ、買います。
If it's cheap, I'll buy it.
どうすればいいですか。
What should I do?
と in a nutshell
と says that whenever the first thing happens, the second follows as a natural, unavoidable result. Attach it to the plain non-past form: 押すと, 寒いと, 静かだと, 雨だと.
It is the natural choice for machines, nature, habits and directions. Because the result is automatic, the second half cannot express your will: no requests, invitations, “let’s”, or “I want to”.
このボタンを押すと、ドアが開きます。
When you press this button, the door opens.
まっすぐ行くと、右に銀行があります。
If you go straight, there's a bank on the right.
春になると、桜が咲きます。
When spring comes, the cherry blossoms bloom.
なら in a nutshell
なら means “if it’s the case that X” or “if you’re talking about X”. It usually responds to something the other person said or to a situation you both know about, and then gives advice, an opinion or a decision. Attach it to the plain form of verbs and い-adjectives, or directly to nouns and な-adjective stems: 行くなら, 高いなら, 学生なら.
The key difference from the others: with なら the second action can happen before the first. “If you’re going to Kyoto, book a hotel” means book it now, not after you arrive.
京都に行くなら、早めにホテルを予約したほうがいいよ。
If you're going to Kyoto, you should book a hotel early.
A：パソコンが欲しいんだけど。B：パソコンなら、秋葉原がいいよ。
A: I want a computer. B: If it's a computer you want, Akihabara is the place.
眠いなら、もう寝たら？
If you're sleepy, why not go to bed?
Side-by-side examples
✅ 駅に着いたら、電話してください。
❌ 駅に着くと／着けば、電話してください。
Call me when you get to the station.
A request needs たら. と can never take one, and ば can’t here because 着く is an action done by the same person who will call.
京都に行くなら、新幹線の切符を買っておいて。
京都に行ったら、八ツ橋を買ってきて。
If you're going to Kyoto, get the shinkansen tickets (beforehand). / When you're in Kyoto, bring back some yatsuhashi.
なら lets the second action come first. たら means you do it after arriving. The tickets have to be bought before the trip, the souvenirs during it.
春になると／なれば／なったら、桜が咲きます。
When spring comes, the cherry blossoms bloom.
All three are fine. と sounds most natural for something that happens every year, ば stresses the condition, and たら sounds a little more like one particular spring.
✅ 安ければ／安かったら、買います。
✅ （そんなに）安いなら、買います。
❌ 安いと、買います。
If it's cheap, I'll buy it. / If it's (that) cheap, I'll buy it.
ば and たら make a condition out of the price. なら reacts to a price someone just told you. と fails because “I’ll buy” is a decision, not an automatic result. The habitual version works, though: 安いと、つい買ってしまう (“When something’s cheap, I end up buying it”).
✅ 窓を開けたら／開けると、雪が降っていた。
❌ 窓を開ければ、雪が降っていた。
When I opened the window, it was snowing.
For something you did once and then discovered, use たら or と. ば and なら describe conditions, not things that already happened.
How to choose
- Is the second half a request, invitation, suggestion or “I want to / I’ll”? Rule out と. If the first half is an action by the same person, rule out ば too.
- Does the second action happen before the first (buy tickets before the trip)? Use なら.
- Are you responding to what someone just said or to a known situation (“if that’s so…”)? Use なら.
- Is it a machine, a law of nature, a habit or directions? Use と.
- Are you asking for or giving advice with いい? Use ば or たら (どうすればいい／どうしたらいい).
- Is it something that happened once in the past, followed by a discovery? Use たら or と.
- Still unsure? たら is right far more often than the others.
Common mistakes
と describes automatic results, so it can't carry a request like “let me know”.
たら puts the purchase after arrival. Only なら lets the advice apply before the trip.
なら doesn't express “after”. For a plain sequence of events, use たら.
ば sets up a condition. It can't narrate a single past event and what you found.
Practice: choose the right one
Show answer
終わったら: “Once your homework is done, you can go out and play.” The homework has to be finished first, and the second half grants permission, which rules out と.
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と: “If you turn right on this street, there's a post office.” Directions are the classic と case. 曲がったら is also acceptable.
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なら: “If you're going to Hokkaido, you should buy a warm coat.” B is responding to A's plan, and the coat has to be bought before the trip.
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寝れば: “If you went to bed earlier, you'd be able to get up in the morning.” The form 寝れ〜 already gives it away, and ば fits the focus on what you'd need to change.
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開けたら (or 開けると): “When I opened the fridge, there was nothing in it.” A single past action followed by a discovery takes たら or と, never ば.
Related grammar to review next
- たら: if; when; after — the full lesson on the all-purpose conditional
- ば: if; when a condition is met — conjugation tables for every verb group and 〜ばいい
- と: when; if; naturally results — more on automatic results and discoveries
- なら: if; when it comes to — the topic-raising uses of なら
- たらどう: why not try; how about — the suggestion pattern built on たら
- もしも〜たら: if; supposing — how もし and もしも strengthen a hypothetical
- とすれば・としたら・とすると: if; assuming that — the N3 “assuming that” conditionals built from と, ば and たら
FAQ about たら vs ば vs と vs なら
What is the difference between たら and ば and と and なら?
All four translate as “if”, but they carry different logic. たら is the safe default: “if/when X happens, then Y”, and it works with any kind of main clause. ば puts the spotlight on the condition itself (“only if X”). と describes a result that follows automatically, every time.
How do I choose between たら and ば and と and なら?
Is the second half a request, invitation, suggestion or “I want to / I'll”? Rule out と. If the first half is an action by the same person, rule out ば too. Does the second action happen before the first (buy tickets before the trip)? Use なら. Are you responding to what someone just said or to a known situation (“if that's so…”)? Use なら.