About the Gear Ratio Calculator
A gear ratio tells you how a pair of gears trades speed for torque. Divide the driven gear’s teeth by the driver’s: a ratio above 1 means the output turns slower but with more torque. This calculator also handles bicycle gearing and shows the resulting output speed and torque.
Also known as: gearing calculator, gear teeth ratio, bicycle gear ratio, sprocket ratio, drive ratio.
How to use this calculator
- Enter driving gear teeth, driven gear teeth, input speed, input torque 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.
Formula
ratio = driven teeth ÷ driving teeth
Worked example
Using the values pre-filled in the calculator above:
- Driving gear teeth = 15
- Driven gear teeth = 45
- Input speed = 1,500 RPM
- Input torque = 20 N·m
- Efficiency = 97 %
the calculator returns:
- Gear ratio: 3 : 1
- Output speed: 500 RPM
- Output torque: 58.2 N·m
- Type: Reduction — slower, more torque