Early and accurate measurement of software products is an essential prerequisite for successful estimation and control of software development projects. Existing measurement techniques, however, are inadequate in the context of newly emerging object-oriented modelling approaches. This paper proposes a new measure, the System Meter, which is simple and intuitive, formally sound, takes reuse explicitly into account and can be easily automated. Empirical studies have shown that the System Meter is a better effort predictor than the well-known Function Points.