Calculate derives from the Latin word for "count." When you calculate, you either count something up or calculate on something happening. You might be able to calculate the answer to a simple equation in your head but need a calculator to figure out a more complex problem.
We calculate that the average size farm in Lancaster County is 65 acres. [VERB that] A computer calculates by switching currents on or off. [VERB] If you calculate the effects of something, especially a possible course of action, you think about them in order to form an opinion or decide what to do.
From Longman Dictionary of Contemporary English cal‧cu‧lat‧ing /ˈkælkjəleɪtɪŋ/ adjective thinking carefully about how to get exactly what you want, often without caring about anyone else – used to show disapproval He gave her a calculating look.
