Gear Reducing Formulas

Output torque, speed and horsepower when using gears

Gear - transmission ratio

Gear Output Torque

Mo = Mi r μ                               (1)


Mo = output torque (Nm, lbfft)

Mi = input torque (Nm, lbfft)

r = gear transmission ratio

μ = gear efficiency (%)

Example - Geear Output Torque

The output torque from a transmission with input torque 500 Nm, gear transmission ratio 3.8 and gear efficiency 0.9 - can be calculated as

Mo = (500 Nm) (3.8) (0.9)

    = 1710 Nm   

Gear Output Speed

So = Si / r                             (2)


So = output speed (rad/s, rpm)

Si = input speed (rad/s, rpm)

Example - Gear Output Speed

The output speed of a transmission with input speed 2000 rpm and transmission ratio 3.8 can be calculated as

So = (2000 rpm) / (3.8)

    = 526 rpm 

Gear Output Horsepower

Po = Pi  μ                              (3)


Po = output horsepower (W, hp)

Pi = input horsepower (W, hp)

Example - Gear Output Power

The output power from a transmission with input power 300 kW and efficiency 0.9 can be calculated as

Po = (300 kW) (0.9)

    = 270 kW 

Related Topics

  • Mechanics - Forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more

Related Documents

Tag Search

Search the Engineering ToolBox

- "the most efficient way to navigate!"

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your SketchUp model with the Engineering ToolBox - SketchUp Extension/Plugin - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Translate the Engineering ToolBox!
About the Engineering ToolBox!