An image forming apparatus includes an image forming mechanism, an image bearing member, a transfer member, a transfer member mount, and an image detector. The image forming mechanism forms a first image and a second image on a surface of the image bearing member. The transfer member is disposed facing the image bearing member and contactable thereagainst to form a transfer nip at which the first image is transferred from the image bearing member to a recording medium. The transfer member mount on which the transfer member is disposed accommodates multiple different sizes of transfer member. The image detector detects the second image on the surface of the image bearing member. The image forming apparatus includes a plurality of interchangeable transfer members, only one of which at any given time faces the image bearing member, and a transfer member switching device to switch between the plurality of transfer members.