This gear ratio calculator finds the gear ratio from the number of teeth on the driver and driven gears, and optionally the output speed from an input RPM.
Gear Ratio Calculator
Formula
Gear ratio = driven teeth / driver teeth • Output speed = input speed / ratio
How to Use This Calculator
- Enter the number of teeth on the driver (input) gear.
- Enter the teeth on the driven (output) gear.
- Optionally enter the input RPM, then click Calculate.
Worked Example
A 20-tooth driver and 60-tooth driven gear give a ratio of 3:1. At 1500 input RPM the output is 1500 / 3 = 500 RPM.
Frequently Asked Questions
How do you calculate gear ratio?
Divide the number of teeth on the driven gear by the number of teeth on the driver gear.
What does a 3:1 gear ratio mean?
The driver gear turns three times for every one turn of the driven gear, increasing torque and reducing output speed.
How does gear ratio affect speed and torque?
A higher ratio reduces output speed but increases torque; a lower ratio does the opposite.