About the Gear Ratio Calculator
What is the Gear Ratio Calculator?
The gear ratio is the number of teeth on the driven gear divided by the teeth on the driver. A ratio above 1 slows the output and multiplies torque; below 1, it speeds up and reduces torque.
Enter the input speed and torque to see the output values after gear losses.
How to use the Gear Ratio Calculator
- Driver (Input) Gear Teeth (sample: 20)
- Driven (Output) Gear Teeth (sample: 60)
- Input Speed (rpm) (sample: 1,440)
- Input Torque (N·m) (sample: 10)
- Gear Efficiency (%) (sample: 95)
- Press Calculate Gear Ratio (results also refresh as you type). The result card shows the Gear Ratio, along with Ratio as a number, Output speed, Output torque and Type.
Formula used
Ratio = Driven teeth ÷ Driver teeth
- Output speed = input rpm ÷ ratio
- Output torque = input torque × ratio × efficiency
Spur gears are about 95–98% efficient per stage; worm gears can be as low as 50–90%.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| Driver (Input) Gear Teeth | 20 |
| Driven (Output) Gear Teeth | 60 |
| Input Speed (rpm) | 1,440 |
| Input Torque (N·m) | 10 |
| Gear Efficiency (%) | 95 |
| Result | Value |
|---|---|
| Gear Ratio | 3 : 1 |
| Ratio as a number | 3 |
| Output speed | 480 rpm |
| Output torque | 28.5 N·m |
| Type | Reduction – slower, more torque |
Tips for using the Gear Ratio Calculator
- For multi-stage gearboxes, multiply the ratios of each stage.
- Power stays the same through gears apart from losses.