Motors & Motion Calculator

Gearbox Output Torque Calculator

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

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.

Estimate Reducer Output Torque, Output Speed, and Power

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.

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

How to Use This Gearbox Torque Calculator

1. Start with motor torque and RPM

Enter the torque and speed available from the motor or upstream drive before applying the reducer ratio.

2. Enter the gearbox ratio

Use the reducer ratio or calculated gear ratio. Higher ratios increase output torque while reducing output speed.

3. Include gearbox efficiency

Real gearboxes lose power through friction, gear mesh losses, seals, lubrication, and bearings. Efficiency keeps the estimate more realistic.

4. Verify the actual reducer

Compare the output torque and RPM against manufacturer ratings, service factor, duty cycle, thermal limits, and shock load.

Estimate Reducer Output Torque and Speed

Enter motor torque, motor speed, gear ratio, and gearbox efficiency. The calculator estimates output shaft torque, output speed, and transmitted horsepower.

Enter values and press Calculate.

My Saved Calculations

Save setups, reload prior inputs, and reuse common checks.

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Do Not Treat Output Torque as the Final Reducer Rating

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.

A reducer can appear strong enough based on steady-state output torque but still be wrong for the application if the machine has high inertia, frequent start-stop cycles, product jams, indexing motion, reversing loads, or impact conditions.

Use this calculator as a first-pass output estimate, then verify the actual reducer against catalog ratings, application service factor, duty cycle, allowable overhung load, mounting orientation, lubrication requirements, and thermal limits.

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.

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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