calculating profit and loss; mercenary thinking
Often used critically to describe a mindset that weighs everything by personal gain or loss, rather than literal accounting.
彼はいつも損得勘定で動くから、友達が少ない。
He always acts based on profit-and-loss calculations, so he has few friends.
ボランティアに損得勘定を持ち込むべきではない。
You shouldn't bring a mercenary mindset into volunteering.