Defining Belt Drive Efficiency

Belt energy losses are typically considered in terms of shaft speed and torque:

Efficiency (%) = [(Output Torque X Output RPM) / (Input Torque X Input RPM)] X 100

Torque losses occur due to friction and bending stresses. Speed losses result from belt slippage and creep. Note that slip is only a factor for V-belt drives, as it does not occur in synchronous belt drive systems.