Pulley and Belt Size

Calculates pulleys and
belt length to obtain
a desired output RPM.

Pulley and Belt Size

Calculate pulley speeds
and belt length.

Entry Form

Driver: RPM

Driver Pulley: Inches

Driven Pulley:Inches

Distance:Center to Center



Belt Length:Inches

Belt Length:Centimeters


Using This Pulley
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 in a
(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 edge.

Belt calculated length is
calculated from pulley
center to pulley center

Something to Consider

With a two pulley system,
there is a small lose
of power.
When the pulley system
is a gear up arrangement,
there is a greater
power lose.


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Calculate Pulley Sizes,
for a Desired RPM Output
and Determine Belt Length,
at Find N Choose.