Driver tools Power converter: bhp, PS and kW

  • Convert quickly and easily between bhp, kW and PS
  • Learn about the different measures of engine power
  • See the difference between torque and brake horsepower
  • Find out how to check your car's engine power

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Power converter

Carmakers sometimes quote the power outputs of their engines using different units, which can be confusing when you're trying to compare new cars. 

This handy calculator lets you convert quickly and easily between the three main measurements used – bhp, kW and PS.

What is bhp?

Brake horsepower – or bhp – is the most widely used measure of engine power alongside PS (see below), although it's often not clear which unit manufacturers are using in their brochures. 

But it's not all about horsepower - Which? tests every car for acceleration for 35mph to 62mph - read our in-depth car reviews to see what else we test

Unlike ‘horsepower’, which refers to an engine’s total output, brake horsepower only looks at the amount of energy left once other parts like the gearbox, alternator and water pump have all been powered. It's measured at the road wheels, not at the flywheel.

Powerful engines have a higher bhp figure. For example, an entry-level Toyota iQ has a 68bhp engine, while a supercharged Jaguar XF packs 503bhp.

PS explained

Though it’s still commonly used by carmakers, PS or Pferdestärke (horse-strength in German) was actually replaced by kW as the EU's ‘legal’ measurement of engine power in 1992. 

One PS is about 98.6% of a brake horsepower – the two are virtually interchangeable, and PS is sometimes referred to as 'metric horsepower'.

Measuring power in kilowatts

You may see some carmakers quoting the power of their engines in kilowatts – especially on the Continent – but this measurement is used far less frequently than PS or bhp. A kilowatt (kW) of power equates to around 1.34bhp.

So what is torque?

Torque refers to the amount of pulling power an engine delivers when working at different speeds. The more torque an engine has, the more pull (or acceleration) it offers at lower revs.

Torque is nearly always discussed alongside brake horsepower, as it gives clues to how quickly the engine will be able to shift the car’s weight when overtaking or pulling away from traffic lights.

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