We present a prediction model for digital printers and more specifically for electrophotographic devices. On the one hand, we propose an electrophotographic simulation model which estimates the microscopic structure of any printed toner layer based on its input halftone bitmap. Applying BOUGUER-BEER-LAMBERT's law, the obtained spatial toner arrangement yields the spectral transmittance distribution for non-light scattering colors. On the other hand, we introduce an extension to the KUBELKA-MUNK (KM) model, which allows to compute the halftone reflectance spectra from the estimated transmittance spectra. The extended KM model bridges the gap between the mathematical description of the optical point spread function of common office papers and the experimental results of simple reflectance measurements. With the combination of the models, we are capable of predicting the reflectance spectra of a printed monochrome wedge with a mean estimation error of less than CIELAB ΔE*94 = 1.