A method to quantify manufacturing activities for shipbuilding projects is devised, based on extrapolation of historical projects. Extrapolation rules are based on first principles and fine-tuned using empirical data. A 4-tier hierarchical system structure is proposed, incorporating different types of interrelations. Subsequently, it is investigated how design principles can be used to mathematically define these relations, resulting in a substantiated work content estimation model. Several shipbuilding projects, some of which recently executed, were used as data source to support the proposed theory. It is demonstrated that detailed production man hour estimations can be made using limited sets of input data.