An image forming apparatus includes an image forming unit for forming an image, and a toner cartridge detachably attached to the image forming unit for supplying toner to the image forming unit. The image forming apparatus further includes a toner supply control unit for controlling an amount of toner supplied from the toner cartridge to the image forming unit; a remaining toner amount detection unit for detecting a remaining amount of toner in the image forming unit; an image forming unit used amount detection unit for detecting a used amount of the image forming unit; and a control unit for controlling the toner supply control unit to control the amount of toner in the image forming unit according to a detection result of the remaining toner amount detection unit and a calculation result of the image forming unit used amount detection unit.