Provided is an image forming system in which an image forming apparatus is connected to a post-processing apparatus having a function of trimming. The image forming system includes: a repeat setting part that determines either: a setting of a scan size of a scan image per one printed reproduction of the scan image, the one printed reproduction being to be laid out by imposition of the scan image; or a setting of the imposition of the scan image according to the scan size of the scan image; a trimming setting part that determines either: a setting of a card size of cards to be obtained by trimming a recording medium; or a setting of a trimming area for the cards; and a coordination part that coordinates the repeat setting part and the trimming setting part.