shita-toki-vs-shitara

2021年1月11日2026年4月21日

Both した時 (shita toki) and したら (shitara) can translate as “when” in English — but they work very differently in Japanese. した時 describes something that happened at the same time as another event; したら introduces a condition, result, or something unexpected. Confusing them can change your meaning in subtle but real ways. This guide explains both forms clearly with examples, so you can use them with confidence.

Yuka

Rei, I’ve seen した時 and したら so many times but I always second-guess myself. Help!

Rei

Don’t worry — this is one of the most common points of confusion for English speakers. Let me clear it up once and for all!

TOC

At a Glance: した時 vs. したら

Feature	した時 (shita toki)	したら (shitara)
Core meaning	When I did / At the time of doing	When / If / Once (after doing)
Focus	Point in time — simultaneous events	Condition or sequence — result follows
Can express “if”?	No	Yes
Unexpected result?	No	Yes (common use)
Register	Casual to formal	Casual to formal
JLPT level	N4	N4

した時 (shita toki) — “When I Did / At the Time of”

した時 is used to describe something that was happening at the same moment as another action — two things occurring simultaneously. The key is that 時 (toki) marks a specific point in time, so した時 always refers back to a moment when something was already true or happening.

Formation note: verb (past form) + 時. The past-tense verb (した / ~た form) before 時 tells you the action was already completed when the main clause event occurred.

Example 1 — two events at the same time:

起きた時、雨が降っていた。
Okita toki, ame ga futte ita.
When I woke up, it was raining.

Example 2 — describing a past moment:

家に帰った時、お母さんはテレビを見ていた。
Ie ni kaetta toki, okaasan wa terebi wo mite ita.
When I got home, my mom was watching TV.

Example 3 — recalling a state at a specific time:

子供だった時、この公園によく来た。
Kodomo datta toki, kono kouen ni yoku kita.
When I was a child, I used to come to this park a lot.

Yuka

Okay, that example with した時 really helped! I never saw it used that way before.

Rei

Right? Seeing real examples is so much more useful than memorizing a definition. した時 is definitely one of those words you’ll start noticing everywhere.

したら (shitara) — “When / If / Once (Something Happens)”

したら is the conditional/temporal form derived from the past tense (した) + ら. It serves two main functions: (1) expressing a condition (“if you do X, then Y”), and (2) expressing a sequence where something happened after an action and the result was often unexpected. This second use — the discovery nuance — is one of the most important differences from した時.

Formation note: verb (た-form) + ら. This is called the たら conditional. It marks the first action as the “trigger” for what follows.

Example 1 — conditional “if”:

家に帰ったら、電話して。
Ie ni kaettara, denwa shite.
When you get home, call me. (= once you’ve arrived, call)

Example 2 — unexpected discovery:

ドアを開けたら、猫が入ってきた。
Doa wo aketara, neko ga haitte kita.
When I opened the door, a cat came in. (unexpected)

Example 3 — advice / suggestion:

疲れたら、休んでください。
Tsukaretara, yasunde kudasai.
If you get tired, please rest.

Yuka

And したら — is it used in formal situations, casual ones, or both?

Rei

Great observation! したら actually works in both — context is everything. The comparison table coming up should make this super clear.

The Critical Difference: Simultaneous vs. Sequential

した時 describes two things happening at the same point in time. したら describes a sequence where the first event triggers or leads into the second.

Sentence	Pattern	Meaning
家に帰った時、母がいた。	した時	When I got home, my mother was there. (simultaneous)
家に帰ったら、母がいた。	したら	When I got home, I found my mother there. (discovery)
起きた時、雨だった。	した時	When I woke up, it was raining. (same moment)
起きたら、雨だった。	したら	When I woke up, I found it was raining. (noticed after waking)

Can した時 Express “If”?

No — した時 cannot express a hypothetical condition. You cannot use 帰った時 to mean “if I go home.” For that, you must use したら (or もし〜たら). This is one of the most important distinctions: したら can mean both “when (sequence)” and “if (condition)”; した時 only means “when (simultaneous).”

Decision Flowchart

You want to say "when I did X..."
        |
Are you describing two things at the SAME POINT in time?
(X was happening when Y was also happening)
        |
   YES                        NO — you mean "after X happened, Y resulted"
    |                          or "if X happens, then Y"
 した時 (shita toki)           したら (shitara)
"When I did X, Y was          "When I did X, I found Y"
 happening"                    "If you do X, then Y"
(simultaneous snapshot)        (sequence / condition)