Complexity management has become an essential undertaking for enterprise architecture (EA). It strives for an optimal level of complexity to efficiently and effectively use the EA for its intended purposes. The basis for complexity management is measurement, yet no standardized or proven method for EA complexity measurement currently exists, nor is there consensus about the attributes contributing to complexity. Additionally, the many stakeholders involved in an EA all have a different perception of complexity, leading to the notion of subjective complexity. This research aims to incorporate objective and subjective complexity metrics in a single EA complexity measurement model. A systematic literature review has been carried out to make an inventory of existing complexity metrics. Semi-structured interviews were used to gain insights in stakeholder perceptions and subjective complexity attributes. Based on these results, a conceptual model of EA complexity was designed. The constructs in this model have been operationalized with metrics to create a measurement instrument of EA complexity. The model and its operationalization was then validated through expert interviews, and tested during a case study, where it has been applied in practice.