Calculate gear reduction ratio, output RPM and output torque from a ratio, gear teeth or two stages, or find the ratio needed for a target speed or torque.

Ratio = input speed ÷ output speed = driven teeth ÷ driver teeth. Above 1 reduces speed.

For 10:1 enter 10.

Leave blank for speed only. Add it for output torque and power.

Typical value for one spur or helical stage; 100% gives ideal torque.

Optional settings

Gear Reduction Formula

The following equation is used to calculate the output values of a gear reduction.

OT = IT × GR × etaₜotal
ORPM = IRPM / GR
  • Where OT is the output torque
  • IT is the input torque
  • GR is the reduction ratio: input RPM divided by output RPM (equivalently driven teeth divided by driver teeth). A ratio greater than 1 reduces speed; eta_total is overall efficiency as a fraction
  • ORPM is the output RPM
  • IRPM is the input RPM

To calculate output torque, multiply input torque by the reduction ratio and overall efficiency. At ideal 100% efficiency, output torque equals input torque times the ratio. Output RPM is input RPM divided by that same ratio.

Gear Reduction Definition

A gear reduction is defined as the change in torque with respect to a set of interlocking gears.

Gear Reduction Example

How to calculate gear reduction?

  1. First, determine the input torque.

    Measure the input torque.

  2. Next, determine the gear reduction ratio.

    Calculate the gear reduction ratio.

  3. Finally, calculate the output torque.

    Calculate the output torque using the equation above.

FAQ

What is a gear reduction?

A gear reduction is a change in RPM or torque of a rotating object due to two or more interlocking gears. These gears will cause corresponding objects to rotate slower or faster depending on the size of the gears.

What is a gear?

A gear is a circular device that, when paired together with another gear, produces a change in rotation speed due to different diameters.