Cathedrals as very large religious buildings spread worldwide, but in medieval times were peculiar to Europe. It seems that the design of cathedrals often had various symbolic implications. Usually, cathedral floor plans are considered as the first step in the whole construction process, and are related to other parts of the cathedral's construction. Previous literature suggested that complicated geometrical and numerical proportions were found in the measurements. The masons, including the master masons, were not likely to have had a sophisticated understanding of mathematical and geometrical systems. This paper suggests some simple geometric methods which may used in the design of the whole cathedral floor plan, based on the square and its derivative constructions, including golden- section rectangles, v 2 and other root rectangles and sacred cut squares. It is argued that simple methods were adopted by the masons in the planning and design process associated with cathedrals in medieval times.