Method and apparatus for predicting and displaying toner usage of a printer

An improved printer (10) is provided that predicts how many pages can be printed before the toner or ink cartridge (90) becomes empty, and also predicts how much time remains before this toner or ink cartridge (90) becomes empty. This prediction is based upon the previous printing history of the printer while using this particular toner cartridge (90). After measuring the quantity of toner left in the toner cartridge, the toner measuring device provides a "level change" output signal when the remaining toner passes through a predetermined gradation threshold. As each gradation level transition occurs, the printer (10) calculates a new value for the "pages per gradation" variable, and also calculates the number of pages that have been printed since the latest cartridge was installed in the printer, the number of pages printed since the last level or gradation change, and the number of pages or sheets printed between the last two level changes. The printer (10) also can approximate the amount of toner used in printing a particular page of print media to create a Toner Tally for each printed page, which can be used to judge the amount of toner used for one print job and compare that to the amount of toner used for a second print job.