An image forming apparatus includes a sensor configured to detect a remaining amount of a recording agent in a cartridge mounted in the image forming apparatus, an output device configured to output at least one of visual and audio information, and a controller. The controller is configured to, upon a first cartridge being dismounted, store, as a previous remaining amount, a remaining amount of a recording agent in the first cartridge detected by the sensor. The controller is also configured to, upon a remaining amount of a recording agent in a second cartridge that has been mounted in the image forming apparatus after the first cartridge is dismounted decreasing to or below a first threshold value as detected by the sensor, control the output device to output information that varies based on a value of the previous remaining amount.