An image forming apparatus configured to form an image on a sheet includes an image bearing member configured to rotate in a predetermined direction, and an image forming unit configured to form an image on the image bearing member based on image data converted based on a conversion condition. A controller of the image forming apparatus controls the image forming unit to form a plurality of measurement images different in density along the predetermined direction of the image bearing member, detects the plurality of measurement images, and generates the conversion condition based on detection results of the plurality of measurement images. The controller controls the image forming unit to form the plurality of measurement images in a dispersed manner in terms of positions of the plurality of measurement images on the image bearing member in accordance with periodic unevenness that occurs in the measurement images.