We propose a method for power optimization that considers glitch reduction by gate sizing based on the statistical estimation of glitch transitions. Our method reduces not only the amount of capacitive and short-circuit power consumption but also the power dissipated by glitches which has not been exploited previously. The effect of our method is verified experimentally using 8 benchmark circuits with a 0.6 m standard cell library. Our method reduces the power dissipation from the minimum-sized circuits further by 9.8% on average and 23.0% maximum. We also verify that our method is effective under manufacturing variation.