We use this expression to say that we want to join in an activity (IN) or not join in an activity (OUT).
You can use this phrase in ………… language.
Spoken
Written
Informal
Example 1
A: We’re having a squash teambuilding tomorrow. Are you interested?
B: Count me in! I love squash.
Example 2
A: I think we should complain to the manager.
B: Count me out. I don’t want to lose my job.