Calculator Inputs
Enter either gear teeth counts or a manual stage ratio. Multi-stage systems compound both ratio and efficiency.
Plotly Graph
This chart sweeps nearby overall ratios to show the tradeoff between output speed and actual output torque.
Example Data Table
| Case | Driver Teeth | Driven Teeth | Stages | Input Speed | Input Torque | Efficiency | Overall Ratio | Output Speed | Actual Output Torque | Travel Speed |
|---|---|---|---|---|---|---|---|---|---|---|
| Conveyor reducer | 18 | 54 | 1 | 1800 RPM | 120 Nm | 96% | 3.00 : 1 | 600.00 RPM | 345.60 Nm | 33.93 km/h |
| Compact drive | 14 | 56 | 1 | 1450 RPM | 85 Nm | 94% | 4.00 : 1 | 362.50 RPM | 319.60 Nm | 17.08 km/h |
| Two-stage reducer | 12 | 48 | 2 | 3000 RPM | 40 Nm | 92% | 16.00 : 1 | 187.50 RPM | 541.70 Nm | 7.07 km/h |
Formula Used
Stage Ratio = Driven Gear Teeth ÷ Driver Gear Teeth
Overall Ratio = (Stage Ratio)Number of Stages
Overall Efficiency = (Efficiency per Stage ÷ 100)Number of Stages
Output Speed = Input Speed ÷ Overall Ratio
Ideal Output Torque = Input Torque × Overall Ratio
Actual Output Torque = Ideal Output Torque × Overall Efficiency
Input Power (kW) = 2π × Input Speed × Input Torque ÷ 60000
Output Power = Input Power × Overall Efficiency
Wheel Circumference = π × Wheel Diameter
Linear Speed = Output RPM × Wheel Circumference
These equations assume steady-state operation and no slipping. Real systems may also include bearing losses, belt slip, shock loading, and thermal limits.
How to Use This Calculator
- Enter an application name for reference.
- Select the ratio input mode.
- Use either gear teeth values or a manual stage ratio.
- Enter the number of stages in the gearbox.
- Provide input shaft speed and input torque.
- Set an efficiency value for each stage.
- Optionally enter wheel diameter to estimate travel speed.
- Press Calculate Now.
- Review ratio, speed, torque, power, and linear speed.
- Download CSV or PDF for reporting and sharing.
Frequently Asked Questions
1) What does gear ratio mean?
Gear ratio compares output gear size to input gear size. A larger ratio lowers speed and raises torque. A smaller ratio keeps speed higher and torque multiplication lower.
2) Why does output torque increase when speed drops?
Power is tied to torque and rotational speed. When the gearbox reduces speed, torque usually rises. Some energy is still lost through friction, heat, and mesh inefficiency.
3) Why include efficiency per stage?
Real gears are not lossless. Each stage loses some power through friction and churning. Multi-stage reducers compound losses, so overall efficiency must be estimated rather than assumed.
4) When should I use manual ratio mode?
Use manual mode when the reducer specification already lists a stage ratio. It is also useful when you are comparing vendor gearboxes before final tooth counts are known.
5) Can this calculator estimate vehicle speed?
Yes. Enter wheel diameter and the tool converts output shaft RPM into linear speed. This estimate assumes direct drive and no tire slip or additional final-drive changes.
6) Does more stages always mean better performance?
Not always. More stages can deliver high reduction in compact space. They also add complexity, weight, cost, backlash, and efficiency loss. Choose the stage count that fits the duty.
7) What units does the calculator use?
The tool uses RPM for rotational speed, Nm for torque, percent for efficiency, millimeters for wheel diameter, and reports power in kilowatts.
8) Can I use this for belts, chains, or pulleys?
Yes, with care. The math still helps when a transmission has a clear speed ratio. Add realistic efficiency estimates and remember that slip may affect the real output.