君は計算を間違えているよ。

you; buddy; pal; monarch; ruler; sovereign; (one's) master

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

calculation; reckoning; count; forecast

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to make a mistake (in); to commit an error (e.g. in calculation); to confuse; to mistake something for something else

indicates certainty, emphasis, contempt, request, etc.; used when calling out to someone; used to catch one's breath or get someone's attention; yo!