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How to Calculate Gearbox Output Torque

Output torque is one of the most important values in gearbox selection. A useful engineering estimate is T = 9550 × P × η / n₂, where P is input power in kW, η is drivetrain efficiency and n₂ is output speed in rpm.

Core equation

T = 9550 × P × η / n₂

Where:

• T = output torque in Nm
• P = input power in kW
• η = total transmission efficiency as a decimal
• n₂ = output speed in rpm

Example

A 7.5 kW drive with an assumed total efficiency of 0.94 and output speed of 50 rpm gives an estimated output torque of about 1347 Nm. This is a calculation value, not automatically the catalog-rated torque of a specific gearbox configuration.

Why catalog torque can be different

Catalog ratings incorporate mechanical limits, service factor, gear/bearing capacity and the specific configuration. Use the formula for sizing and QA, then confirm a valid selection row.

How this applies to R, F, K and S gear units

The same engineering principle applies across the CHINFAR four-series platform, but the mechanical layout changes: R is inline/near-inline, F is parallel-shaft, and K/S are right-angle families. Use the principle to define the requirement, then select a configuration within the appropriate family.

Related product families

• R Series Helical Gear Unit
• F Series Parallel Shaft Helical Gear Unit
• K Series Helical-Bevel Gear Unit
• S Series Helical-Worm Gear Unit