Device and method to calculate a consumed amount of toner

An image-forming apparatus including a valid signal generator to input print data and a video clock to synchronize the print data, and generate binary image data, a pixel counter to calculate the number of pixels of the print data based on the binary image data, a data stream counter to calculate the number of particular data streams of the binary image data, a coefficient memory to store coefficients with respect to average toner consumption amounts per pixel, a weight memory to store a lookup table containing weights corresponding to percentages of the number of pixels to the particular data streams, and a controller to calculate a percentage of the number of pixels to the number of particular data streams to read out a weight, and calculate the consumed amount of toner by use of the read weight, the number of pixels, and a toner consumption amount coefficient.