An image forming apparatus includes: a line head including multiple ink jet nozzles arrayed in a line direction; a storage device; and a controller circuit configured to determine an image width, the image width being a width of an image to be formed in the line direction, mandatorily eject ink from an ink jet nozzle group before forming the image, the ink jet nozzle group including multiple ink jet nozzles used to form the image having the image width out of the multiple ink jet nozzles, and store the image width in the storage device as a mandatory ejection width.