Explanation
Used to express 'if it comes to...', 'when it becomes the case that...'.
Formation
Verb-casual + となったら / Noun + となったら
Detailed explanation
The ～となったら grammar point is used to describe a situation where, if matters progress to that stage, a certain action or outcome will follow. It’s often translated as 'when it comes to...', 'if it comes to...'.
Examples
Ryokou ni iku to nattara, nizukuri o shinakereba ikemasen.
If it comes to going on a trip, we have to pack.
Shiken ni ochiru to nattara, dou shiyou.
What should I do if I fail the exam?
Kanojo to wakareru to nattara, totemo kanashii desu.
If it comes to breaking up with her, I’ll be very sad.
Kekkon suru to nattara, jinsei ga ookiku kawaru deshou.
When it comes to getting married, life will probably change drastically.
Practice
Grammar content sourced from hanabira.org.