Empirical studies are important in software engineering to evaluate new tools, techniques, methods and technologies. In object-oriented analysis, use case models describe the functional requirements of a software system, so they can be the basis for software measurement and sizing. The purpose of this study is to develop a new metric called Architectural Element Points (AEPoint) that enables to calculate the effort required to develop a software solution, using the 4-Step Rule Set (4SRS) method. This paper describes a case study with 60 undergraduate students grouped in four teams that developed a software system (Web application) for a real customer. In this study, we used the AEPoint metric to estimate the resources needed to develop a software system. The results of the AEPoint and Use Case Points (UCP) metrics and the real software development effort are compared, conclusions drawn and recommendations are proposed.