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Enter any 3 known values to calculate the 4th
For example, if your small pulley is 6" diameter, and spins at 1000 RPM, and you need to find the second pulley size to spin it at 500 RPM, Enter Pulley1 Size 6, Pulley 1 RPM 1000, Pulley 2 RPM 500, and hit Calculate to find the second pulley diameter. Enter inches as decimal or fraction with space or slash. eg: 6.75 or 6 3/4 or 6 3 4 
Multiple Pulleys  RPM Reduction
To calculate multiple pulley sets, where the first driven (large) pulley shaft drives the second driver (small) pulley, and so on, enter first (small) driver pulley RPM and pulley set diameters and centers separated by commas and  as shown below. The RPM of the first driven (large) pulley is transferred to second set small (driver) pulley and so on. The sets of pulleys will be drawn at the bottom of the page with each set RPM reductions and total RPM reduction through all entered sets. In this instance, the initial small driver pulley RPM is 2000. The small pulley diameter is 3", large pulley diameter is 12.5" and centers is 24". The second set small pulley diameter is 4", large pulley diameter is 12" and centers is 12.5". Sets Or claculate identical sets at current diameters, centers and RPM See Also: Chain and Sprocket Calculator 
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