As the major metropolitan areas all over the world have been highly densified with their growing population, it is critically necessary to accommodate the spatial demands for the city life. Due to the limited expansion of a city considering the distance from the center to the boundary, spatial growth has been turned its direction to vertical three dimensional expansion. As the tall buildings are getting popular nowadays and new form-generating technologies are readily available, more daring unconventional shapes of tall building masses are getting wide spread in the design field. This research is focused on the validity of the efficiency of vertical space planning in tall buildings with their various mass shapes. To build a foundation on measuring the efficiency of a specific tall building mass, this research is a preliminary study on the efficiency of the typical floor spaces in the building. Basic argument of the paper is that the mass of a building is directly reflecting the interior space: the shape of the floor and vice versa. For that reason, certain mass implicates actual efficiency of the space inside. The key of the research is to find a way to covert the general term of spatial efficiency based on simple area take-off to more concise calculation of actual usable space.