Tips and Advice

What is horsepower?

Brake horsepower (bhp) is one of the most common units of measurement in the car world. But what exactly is it? Carbuyer explains

Whether you’re reading one of Carbuyer’s fantastic reviews or a car brochure, or perhaps watching a repeat of a popular motoring show, you’ll no doubt have heard of brake horsepower (bhp) as a measurement of how powerful a car is.

While there are other measurements of power described later in this guide, brake horsepower is most commonly used in British car reviews. Generally speaking, the more brake horsepower a car has, the faster it’ll be. But what exactly is brake horsepower? It’s the measurement of the useful power produced by an engine, once the small amount lost to friction in mechanical parts like the gearbox is accounted for.

Different measurements of power

When it comes to any sort of motorised vehicle, you’ll generally find power expressed in one of four ways. As mentioned above, the most common is brake horsepower (bhp), which we use on this website, and horsepower (hp). While they sound the same, brake horsepower is the figure arrived at once the losses from friction have been accounted for. Horsepower measures the engine’s power output on its own.

Additionally, there’s Pferdestärke (literally, the German for ‘horsepower’) or PS, which is especially popular – unsurprisingly – among German and German-owned brands. This is also known as metric or DIN horsepower. One PS is equal to 0.986bhp, so 100PS is the equivalent of 98.6bhp.

The kilowatts (kW) is a metric measure of power that’s become more and more commonly quoted by manufacturers. It’s also used by scientists and engineers. One bhp is equal to 0.7457kW, meaning the kW figure is always lower than the bhp figure.

What does that power figure mean?

The power figure that’s quoted is always the maximum power the engine can produce – usually at a specific amount of revs per minute (rpm). An engine will very rarely (if ever) develop its maximum power across the full rev range. Naturally aspirated engines (those without a turbocharger) will generally produce their maximum power at higher rpm than a turbo engine.

Hopefully, this will help you navigate the minefield of jargon that is brake horsepower, if you’re still flummoxed by the concept of torque, click here to find out more.

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