What is horsepower and why does it matter?
Last updated July 13th, 2023
If you have even a passing interest in cars, there’s a good chance you’ve encountered the term ‘horsepower’.
It’s a metric of power that is frequently used in automotive circles, although not everyone is familiar with its meaning, which can sometimes lead to confusion.
In this guide, we will clarify exactly how horsepower is defined. We’ll cover the history behind the term and explain how horsepower (hp) differs from brake horsepower (bhp) - another common term in the automotive sphere.
Finally, we’ll provide a glossary of commonly used car power metrics (including variations of the term ‘horsepower’) to help you cut through the industry jargon.
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What does horsepower mean?
Horsepower (HP) is an imperial unit of power that is equal to 550 foot-pounds per second (or around 750 watts). In automotive terms, horsepower is used to calculate how fast force is produced from a vehicle’s engine - and how quickly it can accomplish the work.
The history behind horsepower
The term ‘horsepower’ was coined by Scottish inventor James Watt.
When he reimagined existing steam engine designs in 1776 to improve performance and fuel economy, he needed a way to sell his new engine’s capabilities to a market that was literally driven by horses.
We think you’ll agree ‘horsepower’ is a perfectly apt term for the metric that would ultimately demonstrate Watt’s engine’s superiority over existing horse-drawn vehicles.
What is the difference between HP and BHP?
Traditionally in the UK, brake horsepower (BHP) is used to measure a car’s power. Horsepower doesn’t take into account the frictional losses in power from an engine, whereas brake horsepower does.
This means HP is always higher than BHP. The difference between the two is small on a 1:1 basis, but when you scale it up, they become more pronounced.
A car with 300hp, for example, would have 296bhp. Power figures are typically published in the HP format, but a lot of traditional car magazines still convert to BHP.
How is horsepower measured?
Horsepower is measured as the equivalent of energy expended by a single horse raising 33,000 pounds of water one foot in the air, from the bottom of a 1,000 foot deep well in 60 seconds.
Whilst this is a difficult thing to imagine (and an even more difficult experiment to carry out), a device called a dynamometer is used to calculate this force.
Horsepower and car performance
The more horsepower a car has, the faster it can go in a straight line.
Imagine a car being pushed by a person, then think about how much faster and easier it would be if there were two people pushing.
However, it’s important to note that horsepower isn’t as straightforward as this. For instance, upgrading a 100hp car to 200hp wouldn’t make it twice as fast. (Other factors such as grip, aerodynamics and weight also come into play here.)
What’s more, horsepower also has less of an effect the higher your speed is, with aerodynamic efficiency playing a key role as you get faster.
Horsepower and torque
An engine’s output is measured by horsepower and torque. Torque is the turning force that an engine can exert, whilst horsepower measures how fast an engine can perform the work.
Diesel engines, for example, usually have more torque and less horsepower, whereas the opposite applies with petrol cars.
Horsepower examples for different car types
The average horsepower for a standard vehicle sits at around 180hp. A car’s horsepower may be lower or higher than this figure depending on the vehicle type.
Averages sit at around 170hp for midsize vehicles, 200hp for crossover vehicles – and 240hp for small SUVs.
Other names for horsepower
- PS: This stands for ‘pferdestarke’ in German, which is a literal translation of the word ‘horsepower’. ‘PS’ is most commonly used in Europe.
- CV: This is a French acronym, which stands for ‘chevaux-vapeur’. CV is another direct equivalent to horsepower.
- bhp: The term ‘brake horsepower’ should be familiar to any readers of UK car magazines. Unlike hp, bhp takes into account the impact of braking on power.
- kW: This stands for ‘kilowatt’ and is used in Europe for electric car power outputs. 1kW is the equivalent to about 1.3hp.
Need to convert from ps, kW or bhp? Try our free car power converter tool.
Considering horsepower when buying a vehicle
Horsepower fundamentally impacts how your car performs on the road in relation to its ability to accelerate. So, if you regularly drive on motorways, you’ll likely want a more powerful engine than say, if you mainly drive within the city.
Drivers who regularly tow caravans and trailers will also want a higher horsepower, as the extra weight will require more power to get things moving.
How do I check horsepower on a car?
To calculate how much horsepower (hp) your car's engine produces, use the following formula:
Engine rpm x torque ÷ 5252
Frequently Asked Questions
This is a subjective question - and the answer will also depend on the type of car you are evaluating. Factors such as weight, mechanical grip, aerodynamics and the purpose of the car need to be accounted for.
Yes, this is possible, but requires modification of the engine.
The most common method for modifying an engine is ‘chipping’. This may mean reprogramming the car’s electronic brain to:
- Feed more fuel into the cylinders.
- Change when the spark plugs ignite the fuel.
- Increase how hard a turbocharger blows.
Although engine modification can improve performance, it may also increase strain on the engine. It is also highly likely that modifying your engine will invalidate your car warranty – and affect your insurance premiums.
Yes, in standard driving conditions, higher horsepower cars will use more fuel than standard vehicles.
The following cars have 1600hp or above:
- Bugatti Chiron SS.
- Hennesy Venom.
- Rimac Nevera.
- Lotus Evija.
- Deus Vayanne.
- Devel Sixteen.
Yes, EVs have horsepower.
An electric motor, powered by batteries, can exert horsepower that is expressed and measured in the same way as petrol and diesel cars.
However, electric cars deploy their power in a different manner. Unlike their combustion engine counterparts, they don’t need to be revved out to achieve optimal speed - and therefore, can deliver maximum output immediately.
One unit of horsepower equates to 33,000 foot-pounds of work per minute, which means the power necessary to lift a total mass of 33,000 pounds one foot in one minute.
‘PS’ is simply the more commonly used term for horsepower in Europe - and therefore has exactly the same meaning.
