This is a multifamily residential development calculator that estimates how many apartment units can fit on a given site based on building dimensions, unit mix, and efficiency factors. The tool uses weighted average unit sizes (780 SF for 1-bedroom, 1,100 SF for 2-bedroom units), applies circulation factors for common areas like hallways and stairs, and calculates total units by dividing the usable floor area by the average unit size adjusted for building efficiency. It also accounts for site constraints by subtracting the building footprint plus a 10% landscape buffer from the total site area, and estimates parking requirements at 420 square feet per space including drive aisles and maneuvering areas.