Usable floor area is one of the most important spatial attributes of buildings and premises. It is used, for example, to determine the basis for their taxation. Unfortunately, the question of proper determination of usable floor area in Poland has remained problematic for many years, which is closely related to the occurrence of various definitions of usable floor area in the currently binding legal acts. Consequently, usable floor area is not a universal attribute. This means that in certain cases significant discrepancies may occur between the usable floor area of the same structure, determined for different purposes. In addition, despite attempts made to unify the principles for the performance of surveys of building structures and their parts, this requirement still can not be recognized as fully met. Therefore, there is no doubt that the problem of reliability and availability of data defining the usable floor area of buildings is becoming even more important in view of the introduction of the ‘ad valorem’ tax, which has been planned for years. For this reason, this paper proposes a universal, multi-variant method of estimating usable floor area based on geometric and descriptive data of buildings contained in the cadastre. The Authors, taking into account the applicable legal regulations, have considered the possibilities of practical implementation of individual variants of this specific method. They have carried out empirical tests of effectiveness of the proposed approach. They have also defined tasks for which this method of determining the usable floor area of buildings would be particularly useful.