The estimate of inductor equivalent series resistance (ESR) is required for different aspects of dc-dc converter operation such as power sharing among parallel converters, current-sensorless sensing, compensator tuning. Due to application specific constraints e.g. measuring point accessibility, and variation in operating conditions, the value of ESR cannot be directly measured using a meter and has to be estimated indirectly. This work presents a generalized method for estimating ESR in dc-dc converters using a series combination of a measuring resistor and a switch (R-Sw). This R-Sw arrangement can be either part of the converter, or can be within a separate meter, and can be used with the existing closed loop control system to determine ESR. The theory of operation, design and digital-implementation aspects of the proposed approach has been presented with respect to dc-dc converter topologies. The methodology is illustrated using buck and boost topologies.