The invention relates to a sheet conveying apparatus and an image forming apparatus. The sheet conveying apparatus includes a sheet conveying unit including a drive roller and a driven roller; a downstream detection unit and an upstream detection unit; a conveying amount measuring unit that measures a conveying amount of the sheet; and a conveying distance calculation unit that calculates a conveying distance of the sheet, wherein a distance between the downstream detection unit and the upstream detection unit or a perimeter of one of the drive roller and the driven roller is set such that an expected conveying distance calculated based on a set sheet length of an expected value of the sheet becomes a substantially integer multiple of a perimeter of the one of the drive roller and the driven roller.