Belts & Pulleys
Belt Length Calculator
Enter the two pulley diameters and shaft center distance to estimate the required open-belt length.
Inputs
Formula
Open-belt length approximation
Worked example
Using the default values shown in the calculator, the same formula gives the following result. This is a quick sanity check for the calculation, not a design recommendation.
Inputs
- Large pulley diameter
- 200 mm
- Small pulley diameter
- 100 mm
- Center distance
- 500 mm
Result
- Estimated belt length
- 1,476.24 mm
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Frequently asked questions
What formula does this belt length calculator use?
It uses the common open-belt approximation based on center distance and the two pulley diameters.
Can I mix millimeters and inches?
Yes. Each length input is converted to a common base unit before calculation.
Is this the exact belt size to buy?
Use it as a design estimate. Actual belt selection can depend on pitch line, groove geometry, tension allowance, and available standard sizes.