We present an experimental technique to characterize backscattering in silicon microring resonators, together with a simple analytical model that reproduces the experimental results. The model can extract all the key parameters of an add-drop-type resonator, which are the loss, both coupling coefficients and backscattering. We show that the backscattering effect strongly affects the resonance shape, and that consecutive resonances of the same ring can have very different backscattering parameters.