Physics
Output torque
Torque rises in proportion to the ratio, in the opposite direction to speed. The two changes cancel so that power is conserved.
The Formula
torque_out = torque_in x i
Torque rises in proportion to the ratio, in the opposite direction to speed. The two changes cancel so that power is conserved.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| torque_in | Input torque | newton metres | Turning force delivered to the driving gear. |
| i | Gear ratio | dimensionless | The same ratio used for the speed. |
| torque_out | Output torque | newton metres | Turning force available at the driven shaft. |
What Each Symbol Means
torque_innewton metres
Input torque
Turning force delivered to the driving gear.
idimensionless
Gear ratio
The same ratio used for the speed.
torque_outnewton metres
Output torque
Turning force available at the driven shaft.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate gear ratio page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Gear Ratio, filed under Science. Every number the guide produces comes from substituting into this one line.