Pulley and Belt Size

This calculator determines pulley sizes
to obtain a desired output RPM.
Simply input driven speed and
pulley sizes. Belt length is also

Pulley and Belt Size

Easily calculate pulley speeds, sizes of pulleys
and belt length.

Entry Form

Driver: RPM

Driver Pulley: Inches

Driven Pulley:Inches

Distance:Center to Center



Belt Length:Inches

Belt Length:Centimeters

How To Use This Pulley
and Belt Size Calculator.

Enter the motor speed in RPMs.

Enter the motor pulley size
in inches.

Enter the driven Pulley size
in inches.

Adjust the drive and driven
pulley sizes, to achieve
a certain RPM output.

More than one stages of pulley speeds
can be calculated (compound drive system).
The output of the first stage, becomes the
input for the next stage.

Note, idler pulleys, have no bearing on
speed changes, they only provide tension
to the belt.


Smaller pulleys have greater chance of
belt slippage.

The smaller the pulley the greater the flex,
of the belt and greater the wear.

Less power is lost where larger pulleys
are used.

Pulleys diameter, is measured across
the pulley, from outside edge , to outside

Belt calculated length is from the outside
pulley diameter width.

Something to Consider
With a two pulley system, there is a
10% lose of power.
When the pulley system is a gear up
arrangement, there is a greater
power lose.

Spocket Calculator

Worm Gear Tooth Calculator

Worm Gear RPM Calculator

Tool Tips for Handy People


© Serving the Internet Community
Since 1998 - All Rights Reserved.

Calculate Pulley Sizes,
for a Desired RPM Output
and Determine Belt Length,
at findNchoose.