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Timing Belt Pulley Sizes and Measurements

A timing belt is mostly used when the rotation of the two different shafts need to be synchronized or are made to rotate simultaneously and in the same manner to effectively run any machine.

Togather, the belt, and the shaft make a timing belt pulley that is of prime importance in many industries, including mechanical and electrical industries. 

Timing belt pulley’s sizes and its measurements are of prime importance for the proper functioning of any machine or instrument. 

Only the right-sized pulley can effectively run any instrument, and that is why great attention and care are needed when selecting the right sizes of a timing belt pulley. 

So, how do you calculate the timing belt pulley sizes and measurements? Here’s all you should know about finding them out.

Sizing The Timing Belt

To size the timing belt, many variables are needed, like the number of teeth in the pulley, the width of the pulley, the material used, and much more. 

Based on the specifications of your project, every manufacturer will give you a different combination of the above-mentioned variables for your timing belt. However, it is best if you do the measurements of the belt yourself, just according to the instrument you are making, to get accurate results.

There are different formulae for selecting the right timing belt’s size, which you may want to study, and do your research accordingly.

Sizing The Pulley’s Shaft

The shaft of the timing belt pulley needs to be determined on one’s personal choices and what machinery they’re making or using the timing belt pulley for. Many manufacturers make the pulley shaft themselves, but they can be made on customized order as well. 

A pulley shaft is determined based on the teeth present on them.

Let’s suppose you need one side of the pulley to be faster than another, say at 2:1 ratio. The proper calculation needs to be done to find this ratio out, and once it's found, looking at the number of teeth on a pulley, this ratio can be fulfilled. 


Length of The Belt

The length of the belt is the next and the most tricky step in finding out timing belt pulley sizes. You will need to have measurements of the distance between the center of the two shafts and the diameter of the pitch for both the pulleys.

To make this measurement easy for purchases, most manufacturers have come up with formulas to calculate the belt length. 



  • C = Center to center distance between shafts
  • D1 = Pitch diameter of larger pulley
  • D2 = Pitch diameter of smaller pulley


For exact measurements, the follwojg formula can be used. 

Please note that these formulas only work in the range of 1-8% (most belts are made in this range anyway). You may need to make slight adjustments to the shaft spacing or pulley diameters if the range does not comply. 

So basically, this is how one can measure the timing belt pulley sizes. Based on your preferences, you may want to talk to a manufacturer and get what suits you the best to make an instrument with full accuracy and precision