Online Tool Store
Pulley Speed Ratio Calculator
Calculate driver and driven pulley speed ratios, belt speed, diameter changes, and RPM outcomes for quick mechanical planning.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
How to use Pulley Speed Ratio Calculator
- Set both pulley diameters and driver RPM, then read ratio, output RPM, and belt speed.
- Review the live visual result and refine the controls for your scenario.
- Save the values you need; all processing remains on your device.
FAQ
Does Pulley Speed Ratio Calculator run locally?
Yes. Its inputs and calculations stay in this browser and are not uploaded for processing.
Can I replace the sample values?
Yes. The sample is ready on load, and every relevant control accepts your own values.
Is the result authoritative?
It is a practical planning estimate or reference. Verify safety-critical, financial, or technical decisions with a qualified source.
What happens to output RPM if the driven pulley is smaller than the driver?
It speeds up - output RPM equals driver RPM times driver diameter divided by driven diameter, so a smaller driven pulley always turns faster than the driver, and a larger one turns slower.
How we compare
| Capability | Online Tool Store | Printed pulley chart | Mechanical CAD package |
|---|---|---|---|
| Driver/driven diameter and RPM controls | Included | Lookup only | Included |
| Live ratio, output RPM, and belt-speed results | Included | Manual calculation | Included |
| Visual two-pulley belt layout | Included | Limited | Detailed simulation |
Best for quick belt-drive estimates at the bench. Use engineering software and manufacturer data for production design, loads, and safety factors.