An image forming apparatus includes: a detection unit that detects a pinch operation that is an operation of increasing or decreasing a distance between two touch positions on a touch panel; an adjustment unit that, upon reception of setting of a size of a non-standard size sheet, adjusts the set size in accordance with the pinch operation; an angle specification unit that specifies, as a pinch operation angle resulting from the pinch operation, an angle formed by a straight line connecting the two touch positions and one of two orthogonal coordinate axes of a coordinate system of the touch pad; and an adjustment amount change unit that changes an adjustment amount for the set size per operation in accordance with whether the pinch operation angle falls within a first angular range or a second angular range that does not overlap the first angular range.