Gear Ratio Calculator
Enter the teeth on the driving and driven gears to calculate the ratio and see ideal speed and torque changes locally.
A QUICK WALKTHROUGH
How to use this tool
- Enter positive integer tooth counts for the driver and driven gears.
- Optionally enter input RPM and input torque in N·m.
- Calculate the ratio and review the ideal output RPM and torque estimates.
Ratio and ideal estimates
The gear ratio is driven teeth ÷ driver teeth. When input RPM is provided, output RPM is input RPM ÷ ratio. When input torque is provided, output torque is input torque × ratio.
Tooth counts define the relationship
Use the gear that supplies motion as the driver and the gear receiving motion as the driven gear. Tooth counts must be positive integers; optional RPM and torque values cannot be negative.
No friction or loss model
Results are ideal estimates and do not account for friction, slip, backlash, bearing losses, gear strength, or transmission efficiency. All calculations run locally in your browser.
GOOD TO KNOW
Common questions
Which gear is the driver?
The driver is the gear connected to the input power or motion. The driven gear receives that motion.
What does a 2:1 ratio mean?
A 2:1 ratio means the driven gear has twice the teeth of the driver. Ideal output speed is half the input speed and ideal output torque is twice the input torque.
Do I need to enter RPM and torque?
No. Tooth counts alone calculate the ratio. RPM and torque are optional so you can estimate only the values you know.
Are the RPM and torque results real-world values?
They are ideal estimates. Actual output depends on efficiency, friction, load, gear geometry, and other mechanical limits.