Pulley & Sheave Size Calculator
Driven sheave size for a target fan RPM.
Enter your values
ⓘ Live results
Results
- Driven sheave diameter
- 8.75 in
- Drive ratio
- 1.944:1
- Check fan RPM
- 900 rpm
Quick answer
Driven sheave diameter equals motor sheave diameter multiplied by motor RPM divided by target fan RPM.
D_driven = D_motor x RPM_motor / RPM_fan
How to use the Pulley & Sheave Size Calculator
- 1Enter the motor sheave diameter and motor RPM (usually 1750 or 3450 rpm nominal).
- 2Enter the target fan shaft RPM from the fan curve.
- 3Order the nearest stock driven sheave to the calculated diameter.
Worked example
Using the values the calculator loads with:
Inputs
- Motor sheave diameter4.5 in
- Motor RPM1750 rpm
- Target fan RPM900 rpm
Results
- Driven sheave diameter8.75 in
- Drive ratio1.944:1
- Check fan RPM900 rpm
Frequently asked questions
What if only stock sizes are available?
Pick the closest stock size and recompute the resulting fan RPM to check it is acceptable.
Does belt slip affect this?
Assume 1-2% slip for V-belts; synchronous belts have essentially no slip.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.