About the Compound Gear Ratio Calculator
Overall ratio of a multi-stage gear train, with output speed and torque at each stage.
Also known as: gear train ratio, multi stage gearbox, total gear reduction, gearbox ratio.
How to use this calculator
- Enter stage 1 driver teeth, stage 1 driven teeth, stage 2 driver teeth, stage 2 driven teeth and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Compound Gear Ratio formula
total ratio = ratio₁ × ratio₂ × ratio₃ …
Worked example
Using the values pre-filled in the calculator above:
- Stage 1 driver teeth = 12
- Stage 1 driven teeth = 36
- Stage 2 driver teeth = 15
- Stage 2 driven teeth = 45
- Stage 3 driver teeth = 0
- Stage 3 driven teeth = 0
- Input speed = 3,000 RPM
- Input torque = 5 N·m
the calculator returns:
- Overall ratio: 9 : 1
- Output speed: 333.33 RPM
- Output torque: 45 N·m
- Stages: 2