An image reading apparatus includes a tray, first sensors configured to acquire information related to a maximum size of sheets placed on the tray, a scanner configured to generate first image data for each of the sheets conveyed from the tray based on the maximum size, a sheet conveyor configured to convey the sheets placed on the tray toward the scanner, second sensors configured to acquire information related to an actual size of each of the sheets conveyed by the sheet conveyor, and a controller. The controller converts for each of the sheets having an actual size that is different from the maximum size, the first image data stored in a first memory region into second image data based on the maximum size and the actual size of the sheet, and stores the second image data in a second memory region which is different from the first memory region.