となると

expression

when it comes to ...; where ... is concerned

Follows a noun and introduces a topic, often implying that the situation naturally leads to a certain result or characteristic.

• 彼かれとなると、話はなしが長ながくなる。

  When it comes to him, the conversation gets long.

• 日本にほんの夏なつとなると、やはり花はな火び大たい会かいですね。

  When it comes to Japanese summer, it's definitely the fireworks festivals.

expression, conjunction

if it turns out that ...; in that case

Follows a clause and presents a hypothetical or realized condition, often with a sense of 'if that's the situation'.

• 明日あした雨あめとなると、試し合あいは中ちゅう止しだ。

  If it turns out to be rainy tomorrow, the game will be canceled.

• 彼かれが来こないとなると、計けい画かくを変かえなければ。

  If it's the case that he isn't coming, we'll have to change the plan.