Belt and Pulley Ratio Calculator

Find the ratio of a simple Belt and Pulley drive with this Belt and Pulley Ratio Calculator.

Drive Pulley Radius :
Driven Pulley Radius :

Fill in the radius of both pulleys to calculate the total ratio.
Mechanical power travels from the Drive Pulley to the Driven Pulley.

How do you calculate the belt pulley ratio?

The ratio in a drive system is represented in reference to the number 1. A ratio of 2 to 1 would be signified by 2:1. A ratio of 1/4 to one would be signified by .25:1.

To find the total ratio, use the pulley ratio formula:

Ratio = (Radius of Driven Pulley) / (Radius of Drive Pulley)

Example: A handcrank is attached to a drive pulley of 2 inches in radius.
The belt runs from the drive pulley to a driven pulley.
The driven pulley is 6 inches in radius and is attached to a paddle that
churns butter. What is the total ratio of this belt and pulley drive?

Ratio = 6 / 2

Calculated out this gives a ratio of 3:1 . For every 3 revolutions of
the handcrank, the paddle attached to the driven pulley will move
1 revolution.

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