This paper presents the mathematic governing the load and no-load related losses in HMC multi-mode hybrid transmission. The losses of either each component or transmission system contain only mechanical those of it not electrical. The losses of each component are developed as functions or equations based on published information as well as empirical test data and total loss of the transmission system are evaluated under each input conditions such as different input torque, speed, and ATF temperature. The evaluated total losses in each transmission operating mode are examined with empirical no-load test data in order to validate the theoretical approach.