Gearbox Output Torque Calculator

Calculate reducer output torque, output speed, and transmitted horsepower using motor torque, motor speed, gear ratio, and gearbox efficiency.

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Good starting use case: enter motor torque, motor speed, gear ratio, and gearbox efficiency to estimate output shaft torque and speed before checking service factor, shock load, and thermal limits.
Calculator

Estimate Reducer Output Torque and Speed

This calculator is useful for motor and reducer selection, conveyor drives, rotary mechanisms, servo systems, and torque multiplication estimates.

It helps estimate reducer output torque, output speed, and transmitted horsepower for motors driving gear reducers. It is useful for conveyor design, rotary indexing tables, automation machinery, servo drives, and industrial power transmission systems.

Quick examples
Enter values and press Calculate.

Need help applying this to a real machine?

Get connected with a qualified automation integrator if you are sizing a reducer, matching a motor to a conveyor, or checking whether a gearbox can support a real application.

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Output torque is estimated as motor torque multiplied by gear ratio and efficiency. This is a practical engineering estimate and does not account for shock loading, service factor, thermal limits, backlash, or peak acceleration loads.

What to verify after this

This calculator is great for a first-pass estimate, but real gearbox selection still needs more review. After getting output torque and speed, you should check service factor, allowable overhung load, duty cycle, acceleration demand, and the manufacturer’s continuous and peak ratings.

This matters even more in conveyors, indexing tables, and high-inertia systems where startup loads or repeated reversals can stress the reducer far more than steady-state calculations suggest.

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What this calculator gives you

  • Estimated output torque
  • Output torque in lb-in and lb-ft
  • Output shaft speed
  • Estimated output horsepower

Common uses

This helps with reducer sizing, conveyor design, rotary mechanisms, servo applications, and confirming whether the selected transmission gives enough torque multiplication.

Common next checks

  • Reducer service factor
  • Thermal rating
  • Startup and acceleration loads
  • Backlash requirements
  • Shock and duty cycle effects