Gear Ratio Calculator — Speed Reduction for Dairy Machinery
Free online gear ratio calculator. Calculate the gear reduction ratio from motor and output shaft speeds. Used for gearbox selection in dairy processing equipment.
What is Gear Ratio?
The gear ratio is the ratio of the input shaft speed to the output shaft speed in a gearbox. It tells you how much the speed is reduced and how much the torque is increased.
Gear Ratio = Input Speed (RPM) / Output Speed (RPM)
A gear ratio of 20:1 means for every 20 rotations of the input shaft, the output shaft rotates once. This reduces speed but multiplies torque by ~20× (less efficiency losses).
Applications in Dairy Plants
| Equipment | Typical Gear Ratio |
|---|---|
| Agitator (silo) | 40:1 – 100:1 |
| Screw conveyor | 15:1 – 40:1 |
| Chain conveyor | 10:1 – 30:1 |
| Separator / Cream separator | Direct drive (belt) |
| CIP pump | 2:1 – 5:1 |
| Rotary lobe pump | Direct drive |
| Butter churn | 10:1 – 25:1 |
Torque Relationship
Output Torque = Input Torque × Gear Ratio × Efficiency
As speed decreases, torque increases proportionally. A 20:1 gear ratio with 95% efficiency means output torque is approximately 19× the input torque.
Selecting the Right Gearbox
- Determine required output speed (from equipment specification)
- Know the motor speed (from nameplate)
- Calculate required gear ratio = Motor RPM / Required Output RPM
- Select a gearbox with the nearest standard ratio (e.g., 18.5:1, 20:1, 22.4:1)
- Verify output torque meets load requirements with adequate safety factor
Standard Gear Ratios
Most gearbox manufacturers offer standard ratios in the series: 5, 7.5, 10, 12.5, 15, 17.5, 20, 25, 30, 40, 50, 60, 80, 100:1 and more.