How to Use the Gearbox Output Torque Calculator
A gearbox trades rotational speed for torque — it reduces motor speed while multiplying the torque delivered to the load. This calculator takes the motor's input torque, the gearbox's reduction ratio, and its transmission efficiency, and computes the actual output torque you can expect.
The formula is output torque = input torque × gear ratio × efficiency, the fundamental relationship used in gearbox selection and machine design. A 20:1 ratio theoretically multiplies torque by 20, but friction losses in gear meshing and bearings mean the real output is reduced by the transmission efficiency.
Efficiency varies by gearbox type — helical gearboxes commonly reach 95-97%, while worm gearboxes can drop as low as 50-85% depending on the lead angle and lubrication. Always confirm the exact efficiency figure from your gearbox manufacturer's specification sheet, and size the gearbox with a margin above the driven machine's required torque — plus a service factor for shock loads or frequent start-stop cycles — to avoid premature failure.
Frequently Asked Questions
For a 20:1 reduction, enter 20. The gear ratio equals the input shaft speed divided by the output shaft speed.
Common helical or worm gearboxes run 85-97% efficient, but the exact figure should come from the gearbox manufacturer's specification sheet.