〜としたら／〜とすれば／〜とすると

Meaning

Expresses assuming a matter to be true and then stating the conclusion that follows from that case. It draws out a result from an assumption, in the sense of "if that were so, then naturally this follows." "〜とすると" is also used when naturally proceeding from a premise.

Examples

この話が本当だとしたら、大変なことだ If this story is true, it is a serious matter.
彼が犯人だとすれば、動機は何だろう If he is the culprit, what would the motive be?
全員が参加するとすると、会場が足りない If everyone participates, the venue will not be large enough.
明日が雨だとしたら、予定を変更しよう If tomorrow is rainy, let us change the schedule.