GREYSUN ENGINEERING TOOL
Pulley Speed Calculator
Calculate driven pulley speed using motor RPM, driver pulley diameter, and driven pulley diameter.
RPM
Output Shaft Speed
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RPM
Enter the motor RPM and both pulley diameters, then select Calculate.
Speed Ratio
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Speed Change
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Drive Type
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Formula Used
Driven speed is calculated from the motor RPM and the ratio between the driver and driven pulley diameters.
Output Shaft RPM = Motor RPM × Motor Pulley Diameter ÷ Driven Pulley Diameter
How Pulley Size Affects Speed
A larger driven pulley reduces shaft speed. A smaller driven pulley increases shaft speed, assuming no belt slip.
Use Consistent Units
Each pulley diameter can be entered independently in inches or millimeters. The calculator automatically converts both values before calculating the ratio.
Important:
This calculator assumes an ideal belt drive with no belt slip. Actual speed
may vary because of belt condition, tension, pulley wear, loading, and other
operating factors. Verify equipment limits before changing pulley sizes.
Need Help With a Centrifuge Drive System?
Greysun can help evaluate pulley sizing, belt-drive problems, operating speed, vibration, alignment, and centrifuge performance.