Over the past few years, organizations have faced pressure from stakeholders to implement lean principles in their product development processes. However, the existing methods are not capable of measuring the benefits of adopting lean initiatives in the product development process. This research aims to develop a performance measurement model that can measure the effects of implementing lean in the engineering process. Engineering effort is analyzed in order to identify hidden wastes (e.g. inventory in the form of information about product specifications or engineering errors) in the engineering process. The model has been implemented in a civil design process of an engineering consultant company to validate the general applicability of the new model. The implementation of the model provides visibility on the waste hidden in the engineering process and quantifies that waste. The most significant contribution of this research is the development of new performance metrics and a decomposition chart. Finally, performance metrics are properly linked and the model treats lean as a holistic system, quantitatively measuring performance at different organizational levels.