Pulley Calculator

Your details

Belt drive: two pulleys linked by a belt. Pulley block: rope and sheave system for lifting.
Diameter of the driving (input) pulley.
mm
Rotational speed of the driver pulley (e.g. motor shaft speed).
RPM
Input torque on the driver shaft. Leave at 0 to skip torque and power calculations.
N-m
Diameter of the driven (output) pulley.
mm
Distance between the two pulley shaft centers. Required for belt length calculation.
mm
Driven pulley speedSpeed reduction
725RPM

Output shaft speed in revolutions per minute.

Speed ratio (d1/d2)0.5
Belt speed11.39
Belt length1,718.1
Driven torque20
Transmitted power1.52
Effective belt tension133.3
Driven RPM725
Mechanical advantage-
Effort force (N)-

Driven pulley at 725 RPM (speed ratio 0.500).

  • The driven pulley spins at 2.00x less speed than the driver (speed reduction). Torque increases by the same factor.
  • Belt surface speed is 11.39 m/s. Most V-belts are rated up to 30 m/s (5,900 ft/min); flat belts can reach 50 m/s.
  • Estimated open-belt length: 1718.1 mm. Add 1-2% when ordering to allow for tensioning.
  • Transmitted power: 1.52 kW.

Next stepCheck that your belt speed is within the manufacturer rating, and verify center distance allows proper tensioning (typically 1-2 belt thicknesses of adjustment).

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