It can be expressed in power units, most commonly kilowatt, pferdestärke (metric horsepower), or horsepower.

In terms of internal combustion engines, the engine power usually describes the rated power, which is a power output that the engine can maintain over a long period of time according to a certain testing method, for example ISO 1585.

In general though, an internal combustion engine has a power take-off shaft (the crankshaft), therefore, the rule for shaft power applies to internal combustion engines: Engine power is the product of the engine torque and the crankshaft's angular velocity.

Power is the product of torque and angular velocity:[1] Let: Power is then: In internal combustion engines, the crankshaft speed

by 60: The approximate numerical value equations for engine power from torque and crankshaft speed are:[1][3][4] Let: Then: Then: Then: A diesel engine produces a torque

Let: Then: or using the numerical value equation: The engine's rated power output is 103 kW.