An integrated closed-form model and circuit model are used to compute the conductor thickness-dependent effective relative permittivity εeff(f, t), characteristic impedance Z 0(f, t), dielectric loss α d(f, t) and conductor loss α c(f, t) of a slot line. The circuit model demonstrates dispersion at frequencies below 1 GHz. It also computes the imaginary part of Z 0(f, t). The accuracy of the circuit model is tested against several full-wave methods in the frequency range 0.1-60 GHz for a conductor thickness 3-50 μm. For ε eff(f, t) and Z 0(f, t) the average deviation is <1.36%, for α c(f, t) it is 1.88% and for total loss α(f, t) it is 2.13% against the full-wave methods and EM-simulators.