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.

Need a gearbox configuration for your machine?

Send the required motor power, input speed, target output speed or ratio, expected output torque, mounting arrangement, and any installation drawing available. CHINFAR can use these inputs to narrow the R/F/K/S configuration before final engineering confirmation.

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