An image forming apparatus includes a density detector, a determination unit, and a change unit. The density detector detects a density of a patch image formed on an image carrier over plural places. The determination unit determines whether plural detection results of the density detector are within a threshold. When the number of determination results, by the determination unit, that the density of the patch image is not within the threshold exceeds a predetermined number, the change unit changes (i) a detection timing at which the patch image is detected by the density detector or (ii) a formation position of the patch image on the image carrier.