Tapered slot antennas (TSA) are attractive because of their simplicity and broadband features. Although TSA have been used for several years in industry, their analysis has been restricted to metallic TSA whereas in most cases a dielectric substrate is employed. Also, so far previous analyses have primarily concentrated on pattern computations rather than input impedance. In this paper, the finite element-boundary integral method is employed for modeling practical TSA and input impedance calculations are given.