Science
Two-stage gear ratio
Calculate the speed reduction across two gear meshes with a shared intermediate shaft.
Calculators / Science / Belt and pulley speed
Belt and pulley speed calculator
Find ideal driven-pulley speed and belt speed from pitch diameters.
On this page
Driven speed600rpm
Belt speed7.85m/s
Reduction ratio2.5
Calculator controls
How to calculate
Find ideal driven-pulley speed and belt speed from pitch diameters.
Driven speed =
rpm*d1/d2 rpmBelt speed =
pi*d1*rpm/60000 m/sReduction ratio =
d2/d1Worked example
- Driver pitch diameter (mm): 100
- Driven pitch diameter (mm): 250
- Driver speed (rpm): 1500
- Driven speed: 600 rpm
- Belt speed: 7.85 m/s
- Reduction ratio: 2.5
Assumptions and limits
Use pitch diameters, not outside diameters. Slip, belt stretch, power transmission limits and guard design are excluded.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Find ideal driven-pulley speed and belt speed from pitch diameters. A larger driven pulley turns more slowly when belt speed is shared. This does not select a suitable belt or motor.
When this tool is useful
A larger driven pulley turns more slowly when belt speed is shared. This does not select a suitable belt or motor.
Understanding your inputs
| Input | Example |
|---|---|
Driver pitch diameter (mm) d1 | 100 |
Driven pitch diameter (mm) d2 | 250 |
Driver speed (rpm) rpm | 1500 |
Frequently asked questions
What does this model leave out?
Use pitch diameters, not outside diameters. Slip, belt stretch, power transmission limits and guard design are excluded.
How do I reproduce the example?
Enter the displayed example values in their labelled units. Apply the formula before rounding; change one input at a time to compare scenarios.