An image forming apparatus comprises: a photosensitive member that revolvably moves in a moving direction; an exposure device that exposes a surface of the photosensitive member to a light beam which is controllably activated according to an image signal and scanned on the surface of the photosensitive member in a scanning direction perpendicular to the moving direction thereof, thereby forming an electrostatic latent image on the photosensitive member in correspondence to the image signal; a developing device that develops the electrostatic latent image with a toner to form a toner image; and a toner consumption calculator that counts the number of dots constituting the toner image based on the image signal and calculates a quantity of toner consumed by the developing device based on the resultant count value, wherein the toner consumption calculator calculates a toner consumption based on the count value of the dots weighted according to the number of consecutive dots in the scanning direction, and the magnitude of weighted amount is determined based on toner consumption base data representing a toner consumption on a line-patterned toner image which has a line pattern including a component in the moving direction and being formed with a line width corresponding to a consecutive dot number.