To determine the amount or number of something mathematically. She can calculate the total cost of the groceries in her head.
To estimate or judge something based on available information. He tried to calculate the risks before making the investment.
To plan or design something with a specific purpose or effect in mind. The advertisement was calculated to attract a younger audience.
To suppose, believe, or think; to reckon (chiefly US, dialectal). I calculate we'll reach the town before nightfall.