Abstract: The grinding device for grinding coffee beans comprises an interface for the user for selecting the quantity of ground coffee in a range of values of selectable quantities of ground coffee, an electric motor supplied by mains electricity voltage for driving the grinders, means for measuring the mains electricity voltage and an electronic controller configured to: associate, for each value of a selectable quantity of ground coffee, a series of grinding time values with a series of corresponding values of the mains electricity voltage; acquire a value of a quantity of ground coffee selected by the user via the interface; detect by the measuring means a value of the mains electricity voltage; for the acquired value of a quantity of ground coffee selected by the user, set the grinding time value corresponding to the detected mainly electricity voltage value; and drive the grinders for the set grinding time value.