An image forming apparatus includes a platen on which an original is to be placed, a feeder configured to feed an original placed on a tray, a sensor configured to detect a sheet on the tray, a lamp provided to the feeder, a reader configured to read the original placed on the platen and to read the original conveyed by the feeder, an image forming unit configured to form an image on a sheet, and a controller. The controller is configured to control the image forming unit to form a test image on a sheet, control the reader to read the test image formed on the sheet placed on the platen, control a density of the image to be formed by the image forming unit based on a reading result of the test image.