Torque Calculator
Calculate transmitted shaft torque from power and rotational speed.
Torque: 98.79 N·m
Live concept view — geometry scales with the entered design condition.Torque arrows and the live result update as transmitted power or rotational speed changes.
CALCULATION RESULT
98,793 N·mm
- Input power
- 15.00 kW
- Converted power
- 15.000 kW
- Rotational speed
- 1,450 RPM
How this was calculated
Formula: T = 9550 × P / N, where P is power in kW and N is speed in RPM.
Calculation: 9550 × 15.000 kW ÷ 1,450 RPM = 98.79 N·m.
Effect of the operating point
At the same speed, 10% more transmitted power gives 108.67 N·m (+10%). At the same power, 10% less speed gives 109.77 N·m (+11.1%). These comparisons hold power or speed constant; they do not model a motor torque curve.
ENGINEERING CONTEXT
What transmitted torque tells you
Torque is the turning moment delivered by a rotating drive. Converting known power and speed into torque gives the load basis for a shaft, coupling, key, gearbox, belt or chain-drive check.
WHEN ENGINEERS USE IT
Before sizing a power-transmission component
Use this relation when steady transmitted power and operating speed are known. Calculate torque at the actual component speed: a reducer increases torque as it reduces speed, while efficiency and transient loads still require separate consideration.
ENGINEERING PRINCIPLE
Power and rotational speed
Mechanical power equals torque multiplied by angular speed. With power in kilowatts and speed in revolutions per minute, the practical metric form is:
T = 9550P / NT is in N·m, P is in kW and N is in RPM. For downstream shaft-stress calculations, multiply N·m by 1000 to obtain N·mm.
WORKED NUMERICAL EXAMPLE
15 kW at 1450 RPM
Using the opening example: T = 9550 × 15 ÷ 1450 = 98.79 N·m. The same turning moment is 98,793 N·mm for a millimetre-based shaft calculation.
Interpretation: the result is the nominal steady torque at that speed, not the maximum design torque.
Design input: apply the actual duty, efficiency, overload, start/stop and service factors required by the selected component or standard.
COMMON MISTAKES
Protect the unit chain
- Entering horsepower as kilowatts or using motor nameplate speed instead of the shaft speed after reduction.
- Using N·m directly in a formula that expects N·mm.
- Ignoring transmission efficiency, acceleration torque, shock loading and reversing duty.
LIMITATIONS AND REFERENCES
Use a component-specific design check next
This calculator establishes a steady-state torque only. It does not size a shaft or verify stress, fatigue, keyway capacity, coupling rating, deflection, critical speed or compliance. The governing component standard and manufacturer data remain the final reference.
RELATED CALCULATORS
Continue the power-transmission check
Calculation evidence and source provenance
Automated numerical review: 13 September 2026. Four independently derived reference cases and ten rejection cases pass. The reference method uses P = Tω; comparison tolerance is 0.01% relative, with an absolute floor of 10⁻⁹ N·m. The engine uses the rounded coefficient 9550, which differs from 60000/(2π) by about 0.0074%. These checks do not certify a real-world design.
- TEXTBOOK: OpenStax, University Physics Volume 1, §10.8 — rotational power relationship.
- ENGINEERING HANDBOOK: NIST SP 811, Appendix B.9, Power — mechanical horsepower is approximately 745.6999 W; metric horsepower is a different unit.
- DESIGN ASSUMPTION: 15 kW and 1450 RPM are illustrative operating values, not measured equipment data.
CONTINUE THE REVIEW
Sources, help and traceability
Use the published formula and material context before progressing to a design decision. Report a suspected issue so it can be reviewed against the calculation engine.