When to use this calculator
Estimate speed ratio for a two-pulley belt drive. Ideal no-slip model using effective pitch diameters.
Explore the gears, belts & motion calculators for other questions in this topic. For a related calculation, use the Belt Linear Speed Calculator: Find belt linear speed from pulley pitch diameter and rotational speed.
PUTTING IT INTO PRACTICE
Belt Drive Output Speed: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Driver speed (rpm) | 1,500 |
| Driver pitch diameter (mm) | 100 |
| Driven pitch diameter (mm) | 250 |
| Result | 600 rpm |
- Check the input labels and enter the example values above.
- Apply the relationship: Driven speed = driver speed × driver diameter/driven diameter.
- The result is 600 rpm, rounded for display.
How to interpret your result
Ideal no-slip model using effective pitch diameters.
Use compatible modules and effective pitch dimensions. No-slip and ideal-mesh assumptions omit losses and dynamics. A ratio calculation does not select a safe shaft, belt, bearing or gear rating.
Frequently asked questions
Why is a lead-screw lead different from its pitch?
Pitch is the axial distance between thread forms. A multi-start screw advances by pitch times the number of starts per revolution.
When is the belt drive output speed calculator useful?
Estimate speed ratio for a two-pulley belt drive. Ideal no-slip model using effective pitch diameters.
How do I use the belt drive output speed calculator?
Enter driver speed (rpm), driver pitch diameter (mm), driven pitch diameter (mm). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Driven speed = driver speed × driver diameter/driven diameter.
What should I check before using the result?
Ideal no-slip model using effective pitch diameters.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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