This paper closes a series of papers related to the development and implementation of the concept of Impression Evaluation Method. It provides a complete mathematical apparatus for Impression Evaluation Method in dealing with products, services or activities in order to construct the so called “black box” of the impression formation process. The proposed algorithm is based on the conceptual definition of impression, conceptual model of impression formation process and the concept of Impression Evaluation Method developed in the authors’ previous works. The developed algorithm contains well established and time-tested functions and statements from different areas. Some novel functions related to the implementation of Impression Evaluation Method are developed. The classical desirability function is modified in order to eliminate some shortages related to its usage in the current context. The constructed algorithm is presented in the object-oriented style in order to facilitate to the degree possible its translation into the programming languages. The directions of further research are described.