A discharge amount calculating device for calculating the discharge amount of a fluid from a fluid ejecting apparatus is disclosed, in which the fluid ejecting apparatus is capable of ejecting at least one fluid onto a target at a discharge amount of multiple stages. The discharge amount calculating device includes a plurality of calculating sections that calculate the discharge amount of the fluid at the respective multiple stages based on a bit number of input data, a desired number of calculating sections not exceeding 2n being provided, in which n is a positive integer, and a converting section that converts the inputted discharge amount data of n bits into bit number data corresponding to any one of the plurality of calculating sections, and outputs the converted data to the plurality of calculating sections.