The floor space in a building that is actually under lease. Net leasable area is all the leasable area of a building exclusive of none leasable space such as hallways, building foyers, areas devoted to heating, air conditioning, elevators, and other utility areas. the net leasable area produces the lease income economically supporting the building. For example, a building having 5,000 sq. ft. of area may have a net leasable area of 4,250 sq. ft.