Abstract: An implanted cardiac rhythm management device, such as a pacemaker (pacer) or defibrillator provides a lead impedance measurement of the effective resistance of the leadwire connecting the device to electrodes in the heart. The lead impedance measurement is based on the amount of a voltage droop of a capacitively coupled pacing output voltage pulse over a fixed period of time that is shorter than the duration of the pacing pulse. The lead impedance measurement avoids the need for performing a natural logarithm function by using a look-up table of precalculated scaled resistance values corresponding to particular amounts of voltage droop. The lead impedance measurement is enhanced by performing interpolation and correcting for manufacturing tolerances of the particular cardiac rhythm management device.