We present a tool for measuring the Function Point (FP) software metric from the specification of a software system expressed in the form of an Entity Relationship (ER) diagram plus a Data Flow Diagram (DFD). First, the informal and general FP counting rules are translated into rigorous rules expressing properties of the ER–DFD. Then, the rigorous rules are translated into Prolog. The measures given by the system on a number of case studies are in accordance with those of human experts.