Belt Drive Design Calculator
Design V-belt or flat belt drives. Calculate belt length, speed ratio, belt speed, and tight/slack side tensions for power transmission.
Inputs
in
in
in
RPM
HP
Results
Speed Ratio
2:1
Belt Length
76.65 in
Belt Speed2,749 ft/min
Tight Side Tension94.3 lb
Slack Side Tension34.3 lb
How to Use This Calculator
- Enter the Driver Pulley Diameter in inches — use the pitch diameter for V-belts, not the outside diameter.
- Enter the Driven Pulley Diameter. A larger driven pulley reduces output speed and increases torque (speed reduction).
- Set the Center Distance between shaft centerlines in inches. Aim for 1–2× the sum of the pulley diameters for good wrap angle.
- Enter the Motor Speed in RPM and the Transmitted Horsepower for the application.
- Review the Speed Ratio and Belt Length — use the belt length to order the correct standard V-belt designation.
- Check Tight Side and Slack Side Tensions to verify the shaft bearings and belt are rated for those loads.
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