A power loss prediction method previously developed by the authors was extended to include involute spur gears of nonstandard proportions. The method can now be used to analyze the effects of modified addendum, tooth thickness, and gear center distance in addition to the parameters previously considered which included gear diameter, pitch, pressure angle, face width, oil viscosity, speed, and torque. Particular emphasis is placed on high contact ratio gearing (contact ratios greater than two). Despite their higher sliding velocities, high contact ratio gears can be designed to levels of efficiency approaching those of conventional gears while retaining their advantages through proper selection of gear geometry.