The efficiency maximization of thee phase induction motor operating at rated voltage and under the rated voltage is carried out with the help of JMAG Express. A computer program based on the output equations of three phase squirrel cage induction motor have been developed to check the initial design and performance of the induction motor with the help of graphic user interface (GUI). The output of GUI program is feed in the input targeted values of JMAG Express for parameter calculations and efficiency optimization. To optimize the efficiency as an objective function multiple parameters will be optimized and dimensions of stator and rotor are calculated in terms of sensitivity analysis at efficiency optimization. Calculations of under rated voltages are based on the averages voltages of the three unbalanced phases. The performance of the motor is carried out by considering the copper and aluminum cage rotor respectively. Due to reactive power demand, generally the motors which are designed for the rated voltages, but are operating under the rated voltages away from the utility center. To reduce the energy crises the aim of this research article is to improve the design quality of such type of motors with the help of JMAG Express, which distinguish it from other optimum designed processes based on programming languages, as this software is friendly user.