Methods and devices are presented herein for estimating induction motor inductance parameters based on instantaneous reactive power. The induction motor inductance parameters, e.g., the stator inductance and the total leakage factor, can be estimated from motor nameplate data and instantaneous reactive power without involving speed sensors or electronic injection circuits. In one embodiment, the method includes: measuring voltages and currents; converting the measured voltages and currents into discrete-time voltage and current samples by analog-to-digital converters; synthesizing a complex voltage from the discrete-time voltage samples; synthesizing a complex current from the discrete-time current samples; acquiring and storing motor nameplate data; detecting instantaneous rotor speed by calculating an instantaneous rotor slot harmonic frequency with respect to an instantaneous fundamental frequency; calculating, via an induction motor inductance estimator, the motor's instantaneous reactive power and other intermediate quantities; and outputting the stator inductance and the total leakage factor.