To provide an image forming apparatus and a toner consumption detector where an error in detecting toner consumption is reduced.

Screen-processed dot data is input to a pulse width counter 282. A pulse width of every dot is counted by the pulse width counter 282. The counted value is input to a judgement circuit 283, and it is judged by the judgement circuit 283 in which pulse width area the counted value is included, and then, an enable signal is output in accordance with the judgement result. When the counted value is input from the pulse width counter 282 and the enable signal is received, the input counted value is counted by each counter 2851 to 285n. For example, when finishing counting an amount of one page, the counted value is output to multiplication circuits 2871 to 287n, and a coefficient (1 to n) showing toner consumption per dot is multiplied, and the multiplied value is added by an addition circuit 288. The addition value is output outside as the toner consumption.