Image forming apparatus and toner cartridge

An image forming apparatus comprising:

• an image forming unit for forming an image;
• a toner cartridge detachably attached to the image forming unit for supplying toner to the image forming unit, said toner cartridge having a storage medium for storing information;
• a used toner amount calculation unit for calculating a used amount of the toner;
• a remaining toner amount detection unit for detecting a remaining amount of the toner in the image forming unit;
• a remaining toner amount storage unit for storing a detection result of the remaining toner amount detection unit;
• a toner information writing unit for writing used toner amount information calculated by the used toner amount calculation unit and remaining toner amount information detected by the remaining toner amount detection unit to the storage medium disposed in the toner cartridge;
• a toner information reading unit for reading the used toner amount information and the remaining toner amount information stored in the storage medium disposed in the toner cartridge;
• a replacement detection unit for detecting that the toner cartridge is replaced;
• and
• a control unit for calculating a usable amount of the toner based on the used toner amount information and the remaining toner amount information read by the toner information reading unit and the remaining toner amount stored in the remaining toner amount storage unit.