Torque to Power

The torque an engine produces at a given rotational speed is a basic engine specification. The power output is the torque multiplied by the rotational speed.

Torque to Power


P = Power [kW]
T = Torque [Nm]
N = Engine rotational speed [rpm]

1 PS = 0.73549875 kW = 0.986320 hp (SAE)

Some example engine torque and rpm numbers are interesting to gauge the range of values. You can convert the torque to power given the quoted engine speed.

However, most engines generate peak power at a different engine speed to peak torque. Therefore, be careful when using torque and rpm values to calculate power as it will be just at the peak torque engine speed.

EngineTorque@Speed= PowerRated Power
OS FS-20 3.56cc glow plug engine0.2Nm9000rpm0.188kW0.23kW @12500rpm
Honda GCV160 lawnmower engine9.4Nm2500rpm2.46kW3.3 kW @3600rpm
Ford 1.0 EcoBoost 125PS230Nm1400rpm33.7kW92kW @6000rpm
Ford Coyote 5.0 V8542Nm4500rpm255kW343kW @6500rpm
Wärtsilä-Sulzer RTA96-C 25,600 litre 14 cylinder7,603,850Nm102rpm81,220kW80,080kW1
1: the rated power that is quoted does not match that calculated from quoted torque and engine speed, it appears that the rated torque was measured at 100.6rpm


The torque or turning moment acting on a body is defined as the product of the magnitude of the force and the perpendicular distance of the line of action of the force from the axis about which the body is being rotated.

what is torque

T = Fd


  • T = torque Nm
  • F = magnitude of the force N
  • d = perpendicular distance from the line of action of the force to the axis of rotation m

Torque has the same units as work or energy, however, it is a different physical concept and so to show the difference it is measured in newton metres rather than in joules.

Some typical torque values are given in the examples table below. Note: these are only indicative values.

Operate a Door Handle0.2Nm
Open a jam jar3Nm
Steering wheel torque~6Nm
M6 grade 8.8 bolt max torque11.8Nm
Car wheel nuts100Nm
Lorry wheel nuts450 to 900Nm

OS FS-20 Four-Stroke Model Engine

Bench Running a Small Glow Plug Engine

Running the OS FS-20 engine on glow fuel is interesting. This engine may only have a peak torque of 0.2Nm, but if it backfires under compression when starting it hurts.

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