Pulley and Belt Size

Calculates pulley sizes
to obtain a desired output

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

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
from the outside pulley
diameter width.

Something to Consider
With a two pulley system,
there is about a 10% 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.