Circularity potential in the construction sector, a quality that quantifies the contribution to carbon and resource neutrality, is to be standardised in Europe yet. In order to do so, a harmonised definition and method of calculation that offers transparency is crucial. Simplicity in construction methods, a low-tech approach, and a limited variety and pure use of materials support the development of innovation towards a Circular Economy (CE). The state-of-the art in architecture features both simple and complex constructions, which need to be quantified with respect to their circular performance in light of the European norm. A clear European standardised method and accompanying tool(s) to assess the circularity potential of a building or element will encourage designers to use secondary material, to limit waste production, and to enable multiple life cycles of buildings and elements to preserve primary natural resources. In order to meet the target of a successful CE, firstly, a method to quantify success and inform the architectural design process have to be developed and adopted across Europe. Subsequently, the development of practical assessment tools to measure the circularity potential of building components is an essential step towards the implementation of CE. As a matter of fact, several methods are ready or under development, but none has reached the level to be implemented as a European standard. This study aims to provide answers on what characteristics a harmonised method and practical design tool should contain. Two assessment metrics for circularity, one from Germany and one from the Netherlands, are reviewed to compare their applicability in the design process and point out opportunities for a harmonised European method. Five case studies, comprising prefabricated concrete façade elements, are assessed using both metrics. The results will be used to analyse the metrics’ transparencies and abilities to holistically measure the amount of reused and recycled material in a building’s substance and quantify the recyclability of building products in light of their intended recycling path in the future. The third aspect that is integrally analysed is, therefore, applicability in a design process.