Belt Drive Calculator
Work out the belt length for two pulleys at a given centre distance, the wrap angle on the small pulley, the driven speed and the belt speed. Enter a standard belt length to find the centre distance it needs.
Results
Belt pitch length:
- Speed ratio
- Driven speed
- Belt speed
- Wrap on small pulley
- Wrap on large pulley
- Free span of belt
- Centre distance for the standard belt
L = 2C·cos β + π(D + d)/2 + β(D − d), with sin β = (D − d)/2C. Wrap on the small pulley = 180° − 2β. Belt speed = π·d·n / 60 000.
Speeds ignore belt slip, which is usually 1% to 2% for V-belts. A common layout guide is a centre distance between 0.7 and 2 times (D + d). Check belt speed and wrap angle limits in the belt maker's catalogue.