Methods and systems are disclosed for characterizing the response of a subsurface resistivity measurement to determine a characteristic of a borehole within the subsurface and/or a characteristic of a formation surrounding the borehole. Generally the methods include obtaining subsurface resistivity measurement data with a well tool disposed within the borehole and fitting the obtained resistivity measurement data to an equivalent electric circuit model to determine the borehole and/or formation characteristic. The circuit model of these embodiments is representative of a response of the well tool to borehole and formation parameters. The systems generally include a well tool and an apparatus adapted to be coupled to the well tool. The apparatus includes means for receiving measurement data generated by the well tool, means for storing model parameters representative of a response of the well tool to borehole and formation properties, and means for comparing the received measurement data to the stored model parameters to determine the borehole and/or formation characteristic. The disclosed equivalent circuit model is characterized by an electric circuit having at least one resistor-in-parallel component.