How do you know when to use たら or ば or と or なら?

Use たら for one-time if/when events, including commands, requests, and discoveries. Use ば for general conditional statements, especially recurring or hypothetical if-then patterns. Use と when the result happens automatically or naturally, with no speaker control over the outcome. Use なら when you accept someone's stated plan or situation as a given and then give advice or a conclusion.

JLPT Grammar Comparison

たら vs ば vs と vs なら

All comparisons

How to tell them apart

The core split is about control and timing. と describes an automatic, unavoidable result, so it cannot be used for commands, requests, or volitional main clauses. ば states a general conditional and is also weak for commands. たら is the most flexible: it works for one-time events, discovery, and commands. なら takes an already-raised or supposed situation as its topic and comments on it, so it feels like 'given that X, then Y' rather than a temporal sequence.

たら Use たら for one-time if/when events, including commands, requests, and discoveries.
ば Use ば for general conditional statements, especially recurring or hypothetical if-then patterns.
と Use と when the result happens automatically or naturally, with no speaker control over the outcome.
なら Use なら when you accept someone's stated plan or situation as a given and then give advice or a conclusion.

Grammar point	Meaning	JLPT level
たら tara	used for 'if' or 'when' conditions	N4
ば ba	if; conditional marker	N4
と to	if/when something happens, leading to an expected outcome	N4
なら nara	conditional 'if'	N4

たら tara

used for 'if' or 'when' conditions

たら attaches to the past (ta) form of verbs and i-adjectives, and to nouns or na-adjectives with だった, to make a conditional meaning 'if' or 'when'. It works in both casual and polite speech, and can also appear in wishes or counterfactual statements.

よく聞きいたら、ネタじゃなくてマジボケだったみたいです。

When I asked afterwards it seems he hadn't said that as a joke.
何か私にできることがありましたらお知らせ下さい。

Let me know if there is anything I can do.

Full たら grammar page →

ば ba

if; conditional marker

ば is a conditional ending meaning "if". It attaches to the verb by changing the final -u sound to the -eba form (e.g. 出来る → 出来れば). In the examples it appears in the pattern なければならない, which expresses obligation, "must do".

したいことが出来できなければ出来できることをしなさい。

When you can't do what you want, you do what you can.
あなたはもっと仕事をしなければなりません。

You must work more.

Full ば grammar page →

と to

if/when something happens, leading to an expected outcome

Used after a quoted phrase or thought, と marks what someone says, asks, or thinks before verbs like 言う, 聞く, 思う, and 思った. The quoted part ends in plain form (or a question form) and is followed directly by と.

みんなもそうなのかな、と思おもうことくらいしかできない。

I can only wonder if this is the same for everyone else.
「これはとてもおもしろそうだね」とひろしが言います。

"This looks pretty interesting," Hiroshi says.

Full と grammar page →

なら nara

conditional 'if'

In these examples なら appears in the pattern なければならない (also なくてはならない), which attaches to the negative ない form of a verb. It expresses that something must be done, i.e. the action is required or unavoidable.

明日あしたまでに書かかなければならないレポートがいくつかある。

I have a few essays to write by tomorrow.
明日までに仕事を終えてしまわなければならない。

I must have my work finished by tomorrow.

Full なら grammar page →

たら and ば and と and なら are both JLPT N4 grammar points that Japanese learners often mix up. This page compares all 4 side by side on meanings, usage and example sentences, so you can tell them apart.