そうすると

そうすると
conjunction
if so; in that case; then
grammatical
1. if so; in that case
Draws a logical conclusion from the previous statement.
"The trains aren't running." "In that case, we have no choice but to take the bus."
He's not coming? If so, we need to change the plan.
"I'm moving next month." "In that case, will you go to a new school?"
"The budget isn't enough." "If so, we'll need to think of another approach."
I hear the department head is opposed. If so, this project probably won't be approved.
2. then; and then
Indicates what happened next in a sequence of events.
I opened the window. Then, a cool breeze came in.
I took the medicine. Then, the fever gradually started going down.
I pressed the button. Then, a new message appeared on the screen.
He called out to her. Then, she turned around and smiled.
I opened the door. Then, a cat came flying out from inside.

そうすると connects two statements, drawing a logical conclusion or indicating what happens next. It always appears at the beginning of a sentence, responding to the previous context.

Common patterns

そう (so) + する (to do) + (when/if) = "if one does so" / "when that happens"

Functions

1. Logical conclusion: "If so, then..." — responding to new information
2. Narrative sequence: "And then..." — describing what happened next

Similar words

  • すると: then (more for narrative sequences, slightly more literary)
  • それなら: if that's the case (emphasis on the condition, more conversational)
  • だとすると: if that's true (more hypothetical, formal)
  • ということは: that means (drawing a logical inference)
  • じゃあ: well then (casual equivalent)

Register

Neutral to slightly formal. In casual conversation, じゃあ or それなら is more common.