Conditional 〜たら: The Most Versatile 'If/When' in Japanese
What it means
〜たら is the conditional you'll reach for most often. It means "if" or "when," depending on context: "if it rains, I'll stay home" or "when I finish, I'll call you." The trick is that the second clause hasn't happened yet — たら sets up something that will follow once the first thing is true. It handles hypotheticals, one-time future sequences, and even surprising discoveries about the past, which is why it's the most versatile of Japan's four main conditionals (たら, ば, と, なら).
お金があったら、新しいゲームを買う。
おかねが あったら、あたらしい ゲームを かう。
If I had money, I'd buy a new game.
モチが来たら、一緒に食べよう。
モチが きたら、いっしょに たべよう。
When Mochi comes, let's eat together.
One-time future event = 'when.'
先生に聞いたら、すぐ分かりますよ。
せんせいに きいたら、すぐ わかりますよ。
If you ask the teacher, you'll understand right away.
How to form it
The formation is wonderfully simple: make the plain past (the た-form), then add ら. If you already know the た-form, you're done — every word type works the same way.
| Word type | Plain past | + ら | Meaning |
|---|---|---|---|
| Verb (る) | 食べた | 食べたら | if/when (I) eat |
| Verb (う) | 行った | 行ったら | if/when (I) go |
| Verb (irregular) | した / 来た | したら / 来たら | if/when (I) do / come |
| い-adjective | 高かった | 高かったら | if (it's) expensive |
| な-adjective | 静かだった | 静かだったら | if (it's) quiet |
| Noun | 学生だった | 学生だったら | if (I'm) a student |
Because it's built straight from the past tense, the same sound changes you already know apply: 行く → 行った → 行ったら, 飲む → 飲んだ → 飲んだら. No new conjugation rules to memorize.
"If" — hypotheticals
When the first clause is a condition that may or may not happen, たら means "if." The optional word もし ("if, supposing") often sits at the front to signal a hypothetical:
もし宝くじが当たったら、ヤッタンは家を買う。
もし たからくじが あたったら、ヤッタンは いえを かう。
If Yattan won the lottery, he'd buy a house.
もし flags the sentence as hypothetical.
天気が良かったら、公園に行きたい。
てんきが よかったら、こうえんに いきたい。
If the weather is nice, I want to go to the park.
"When" — one-time future sequences
If the first clause is something that will happen and the second follows it, たら means "when" — first this, then that:
大学を卒業したら、日本で働きたい。
だいがくを そつぎょうしたら、にほんで はたらきたい。
When I graduate from university, I want to work in Japan.
ヤッタンの弟は宿題が終わったら、外で遊ぶ。
ヤッタンの おとうとは しゅくだいが おわったら、そとで あそぶ。
When Yattan's brother finishes his homework, he plays outside.
Requests, commands, and suggestions
This is たら's superpower. The ば and と conditionals don't like a request or command in the second clause, but たら welcomes it freely. So when you want to say "when X happens, please do Y," たら is the natural choice:
駅に着いたら、電話してください。
えきに ついたら、でんわして ください。
When you arrive at the station, please call me.
Request after たら — perfectly natural.
疲れたら、少し休んだらどうですか。
つかれたら、すこし やすんだら どうですか。
If you're tired, why not rest a little?
〜たらどうですか is a soft suggestion.
Surprising discoveries (past たら)
There's one more flavor worth knowing: when both clauses are about the past, たら can express a discovery — you did one thing and then found something unexpected. Here it simply means "when," with a note of surprise:
家に帰ったら、誰もいなかった。
いえに かえったら、だれも いなかった。
When I got home, no one was there.
Past + past たら = an unexpected discovery.
窓を開けたら、雪が降っていた。
まどを あけたら、ゆきが ふって いた。
When I opened the window, it was snowing.
Common mistakes
- Building it from the dictionary form. たら attaches to the plain past, not the dictionary form: 食べたら (✓), not 食べるたら (✗). If you can make the た-form, you can make たら.
- Forgetting だ with nouns and な-adjectives. It's 学生だったら and 静かだったら — the だった is part of the past form. Don't drop it.
- Using と or ば before a request. "When you get there, call me" needs たら: 着いたら電話して. Saying 着けば電話して or 着くと電話して sounds wrong, because と and ば resist commands.
- Confusing たら with なら. なら responds to a topic someone just raised ("if you mean sushi, that shop is good"). たら is for an actual event or condition that will or could occur. They aren't interchangeable.
Quick recap
- Build it from the plain past + ら: 行った → 行ったら, 高かった → 高かったら.
- It means "if" (hypothetical) or "when" (a one-time future event), read from context.
- もし often marks the hypothetical "if" reading.
- It's the only conditional that comfortably takes a request, command, or suggestion afterward.
- Past + past たら can signal a surprising discovery: 帰ったら誰もいなかった.
Your turn
Form 〜たら correctly and choose 'if' vs 'when' from context.
Start the 5-question drill →Frequently asked questions
How do I make the たら form?
Take the plain past (た-form) and add ら. 食べた→食べたら, 行った→行ったら, 高かった→高かったら, 学生だった→学生だったら. If you know the た-form, the conjugation is identical.
Does たら mean 'if' or 'when'?
Both. Context decides: if the first clause may not happen, it's 'if' (もし often appears). If it definitely will happen and the second follows, it's 'when.' 終わったら帰る = 'when I finish, I'll go home.'
What's the difference between たら and ば or と?
All three are conditionals, but たら is the most flexible — it's the only one that easily allows a request, command, or suggestion in the second clause: 着いたら電話して ('call me when you arrive'). ば and と resist that.
How is たら different from なら?
なら responds to a topic or assumption just mentioned ('if you're going to Tokyo, take the train'), while たら describes an actual event or condition that occurs. See the comparison guide for details.
For a side-by-side look at all four conditionals, see 〜と / 〜ば / 〜たら / 〜なら compared.