Abstract: A method of determining an output level of an output stack of print media in an image forming apparatus. The print media is transported, one print medium at a time, to the output stack. A sensor positioned in association with the output stack senses when the output level of the output stack has reached a near full level. At least one physical characteristic of the print media is identified which can affect the stacking of the print media. The number of the print media transported to the output stack is counted after the near full level is sensed. A determination that the output level of the output stack has reached a full level is made, dependent upon each of the at least one physical characteristic and the counted number of the print media.