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Pulley RPM and belt length calculator diagram

Pulley 1		Pulley 2
Size		Size
RPM		RPM
Ratio:

Enter any 3 known values to calculate the 4th

If you know any 3 values (Pulley sizes or RPM) and need to calculate the 4th, enter the 3 known values and hit Calculate to find the missing value.

For example, if your small pulley is 80mm diameter, and spins at 1000 RPM, and you need to find the second pulley size to spin it at 400 RPM, Enter Pulley1 80, Pulley 1 RPM 1000, Pulley 2 RPM 400, and hit Calculate to find the second pulley diameter.

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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 6", large pulley diameter is 12" and centers is 16". The second set small pulley diameter is 7", large pulley diameter is 12" and centers is 18". Sets Or calculate 2 3 4 5 identical sets at current diameters, centers and RPM See Also: Chain and Sprocket Calculator