1 [countable usually plural, uncountable]
when you use numbers in order to find out an amount, price, or value
make/do a calculation
Dee looked at the bill and made some rapid calculations.
by somebody's/some/many calculations
By some calculations, the population will reach 8 million soon.
2 [uncountable and countable]
careful planning in order to get what you want, especially without caring about the effects on other people [↪ miscalculation]:
when you think carefully about what the probable results will be if you do something [↪ miscalculation]