A system and method for calculating a space required for a tenant in a building includes determining the areas of rooms required by the tenant. A circulation factor for each of the rooms based on the area of each room is calculated. The total of the room areas and the circulation factors are added to determine a pure space required by the tenant. The losses in actual usable space are determined for a building and an inefficiency factor is calculated based on these losses. The pure space is multiplied by the inefficiency factor to obtain a building efficiency loss. The building efficiency loss is added to the pure space to obtain the space required for the tenant in the building. The system may be configured on a network computer system or a standalone computer.