Shaft power
Steady-state mechanical power. Efficiency, service factor and starting torque are not applied.
Method
P = Tω and ω = 2πn/60. In convenient units, P(kW) = T(N·m) × n(rpm) / 9549.3.
Worked case: 50 N·m at 1450 rpm is 7.59 kW.
What to write beside the result
A review can only check this figure if the inputs sit next to it. Write the value, the unit and the assumption the form used. A diameter in millimetres and a diameter in metres are not the same reading. A force in kilonewtons divided as if it were newtons is a thousand-fold error.
The result is the arithmetic on this page. It is not a utilisation, not a selected product, and not a clause from a standard. If the number is going into a shared container, name the page, the date and the inputs. The file-name checker does not read the calculation.
Logic: how this figure is built.
How to read a shaft power
Power is torque times angular speed. 50 N·m at 1,450 rpm is about 7.59 kW. The page converts revolutions per minute to radians per second before the product. A torque in kilonewton-metres needs the same care.
The torque is the torque at that shaft at that speed. A gear ratio changes both. Do not multiply a motor torque by a gear ratio and then also multiply by the motor speed.
Efficiency is not applied. A delivered power and a motor nameplate differ by the losses in between.
Use it to check a duty against a nameplate order. It is not a shaft stress and not a key size.
- Related: torque from a force
- mechanical guide
Last checked 3 October 2026. Worked figures are scenarios. See methodology and the disclaimer.