About the Pulley Ratio Calculator
Pulley or sheave ratio from diameters, with driven speed, torque and belt speed.
Also known as: sheave ratio, belt drive ratio, pulley speed calculator, v belt ratio.
How to use this calculator
- Enter driver pulley diameter, driven pulley diameter, driver speed, driver torque.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
ratio = driven diameter ÷ driver diameter
Worked example
Using the values pre-filled in the calculator above:
- Driver pulley diameter = 100 mm
- Driven pulley diameter = 250 mm
- Driver speed = 1,450 RPM
- Driver torque = 10 N·m
the calculator returns:
- Pulley ratio: 2.5 : 1
- Driven speed: 580 RPM
- Driven torque: 25 N·m
- Belt speed: 7.592 m/s