This paper proposes a method for defining the quality of a digital system in terms of measurable parameters of both the specification and a subsequent implementation of the design. Initially, software quality metrics are reviewed together with their application to hardware description languages. Metrics relating to circuit implementations are then discussed, such as device and testing costs, reliability, etc. A set of metrics are then proposed and evaluated for a range of VHDL specifications and the circuits resulting from logic synthesis. Initial results indicate that there is a strong correlation between specification and circuit metrics, so that their ratio may be used as a measure of design quality. Further work is proposed in order to validate the measure over a larger number of examples.