Horsepower Ratings

Determining a belt’s HP rating requires more than just knowing the belt type. Speed, pulley sizes, belt length, wrap angle, and other factors affect the HP rating. Speed affects the HP rating because as speed decreases, torque increases, so the HP rating must also decrease. Larger pulleys improve the belt’s HP rating because less tension in the belt is needed to transmit the torque. Synchronous belt HP ratings are based on having at least 60° of wrap and 6 teeth in mesh. V-belt ratings increase as wrap increases. HP ratings also include a length correction factor. Longer belts have higher HP ratings because they are used with larger pulleys and/or larger center distances, which decreases bending fatigue in the belt.

The easiest method to calculate a belt’s HP rating is by using our software Design Flex Pro or Design IQ. You can also use the tables and equations in our Drive Design Manuals. 

Belt horsepower ratings are used for designing belt drives. Always remember to design a drive with an appropriate service factor based on your application.