In a device for calculating a total amount of toner consumed from a toner cartridge, a first amount of the toner, which is consumed in a first region of a recording medium at which a toner image is formed, is obtained. A time period of which the toner cartridge is in operation is clocked. A second amount of the toner, which is consumed in a second region of the recording medium at which the toner image is not formed, is stored in advance. The second amount is associated with the time period. The second amount is added to the first amount in accordance with the clocked time period, in order to obtain the total amount.