An image forming apparatus is provided which includes a developing apparatus configured to form a developer image; a supply apparatus configured to supply developer to the developing apparatus; a detector configured to detect an amount of developer consumed during an image forming process; and a controller configured to perform an addition calculation for the amount of developer consumed, and for employing a value obtained by the addition calculation and a supply threshold value to determine whether developer should be supplied to the developing apparatus, wherein the controller sets the supply threshold value in accordance with an operating state of the developing apparatus.