HP, BHP, PS, CV: What’s the difference?

HP, BHP, PS – you’ve probably seen these meaningless groups of letters all over the motoring media. We’d put good money on you finding one of these acronyms somewhere in your local paper… If it hasn’t gone out of business, obviously.

But what do they mean? Are they just another acronym designed to make the uninitiated look and/or feel stupid? Or do they have a vital significance? Well, that’s what our handy guide is here to sort out.

What do HP, BHP, PS and CV all stand for?

Put in the most simple terms, all these acronyms refer to horsepower, or the amount of power an engine produces. Faster cars will usually have more powerful engines, and therefore more horsepower.

The reason why they have different acronyms is mostly to do with language. HP stands for the English word horsepower, while PS stands for the German word Pferdestaerke (which means horsepower). CV, meanwhile, is short for the French cheveaux vapeur (also meaning horsepower). BHP is the odd one out, because it isn’t quite the same, but we’ll get onto that in a second.

Remember, horsepower is not the same thing as torque. Torque is usually measured in pound-feet (lb-ft) or Newton-metres (Nm), but can be measured in any combination of units for mass and distance.

So what’s special about BHP?

BHP stands for brake-horsepower, which is also known as imperial horsepower, and that’s slightly different to the ‘metric’ horsepower denoted by the likes of HP, PS and CV.

Brake-horsepower is more commonly used in the UK and USA, and it’s a slightly larger unit than metric horsepower. One brake-horsepower, or 1bhp, is roughly equivalent to 1.01 metric horsepower.

So why do we bother?

Excellent question. Why use two different units when they are almost identical? Well, the answer is mostly down to convention, but consider this: Some hypercars have more than 1,000PS – but that’s only 986bhp. Would it be cynical to suggest that some manufacturers just use metric horsepower because it sounds better?

I’ve seen kW somewhere, too. What’s that all about?

Ah, kW stands for kilowatt. Made up of 1,000 watts (named after Scottish engineer James Watt), this unit is also used to measure engine power. It’s just another kind of unit. One metric horsepower (PS, HP, CV etc.) is equal to around 745.7 watts, or 0.7457 kilowatts (kW), while one brake-horsepower (BHP) is slightly more potent, but it’s still just 0.7355 watts.

This is all very confusing…

Yeah, we know. Which is why, at The Garage, we don’t mix and match. We use HP for power outputs and Nm for torque. So if the manufacturer says a car has 148bhp and our review says 150hp, neither of us is lying; we’re just using different units. The joys of engineering…