Area and volume values of buildings and building parts have been used in many applications including taxation, valuation and land use planning. Many countries maintain a national standard for representing the measurements of floor areas in buildings. The national standards generally use similar basis for measuring building floor areas, in fact, areas specified in national standards often have semantic differences. Therefore, a number of international standards have been developed for harmonizing floor area measurements; however, they also have differences. This study aims at harmonizing the floor areas defined in the international property measurement standards by revealing the semantic relations between them and formalizing them with an ontological approach. To achieve this objective, the international property measurement standards were firstly examined in order to identify semantics, principles and practices in floor area measurements. Then, the obtained information were utilized to develop a set of measurement ontologies for harmonizing the property measurement standards. This paper also investigates 3D data standards to reveal whether they can be utilized for realizing the property measurement standards.