In this paper, we study the Spectrum Use Measure(SUM) model for quantifying the extent of spectrum use by existing radio communication systems. This model calculates the interference level between transmitters and receivers by applying the EMC analysis technique of interference prediction process such as antenna radiation pattern model and propagation model which are well known. While several previous works have described the spectrum resources by constructing the interference contours around existing radio systems, the SUM technique is developed for quantifying and portraying the spectrum resources used by radio communication systems in a geographic area. Computer simula- tion results are illustrated to verify the calculations for the Spectrum Use Bandwidth(SUB) and Spectrum Use Factor (SUF) performed by the SUM model and find the usefulness of the SUM model.