What is horsepower and why does it matter?

What is horsepower, and why does it matter? We break down how it shapes speed, power, and everyday driving performance.

If you know anything about cars, you’ve almost certainly heard the term “horsepower” thrown around. But what is horsepower, really?

In this guide, we break down what this common measure of engine power actually means, how it’s calculated, and whether it has anything to do with horses at all.

Remember, you can buy a brand new or used car right here on Carwow. And you can sell your car, too. We’re here to help you through every step of your car-changing journey.

What is horsepower in cars?

Horsepower (hp) in cars is a measure of how powerful an engine is and how quickly it can do work. In simple terms, it shows how fast a car can accelerate and its potential top speed. Higher horsepower usually means stronger performance at higher speeds.

Here are some terms you need to know that are related to horsepower:

HP/PS/CV

HP stands for horsepower, the standard unit used in the UK and US to measure engine power. 1.34hp is equal to about 1kW.

PS is from the German Pferdestärke, meaning “horse strength.” It’s a close equivalent to horsepower and most commonly used in Europe. 1hp is equivalent to about 1.014PS.

CV comes from the French chevaux-vapeur, meaning “horsepower.” Like PS, it’s broadly equivalent to horsepower and widely used in European car specifications. 1hp is equal to about 1.04CV.

BHP

Brake horsepower is a common term in the UK used to measure an engine’s power output.

kW

This stands for kilowatt and is commonly used in Europe to describe car power outputs, especially for electric vehicles. 1kW is equal to about 1.34hp.

WHP vs BHP: what is the difference?

Brake horsepower (bhp) is measured at the engine. Power measured at the wheels is lower because some is lost through friction and inertia in the gearbox, axles, and wheels. This is why wheel horsepower is always slightly lower than engine power figures like bhp.

Manufacturers today often quote power in horsepower, although some publications and enthusiasts still prefer bhp out of habit.

When comparing cars, the most important thing is to use the same measurement rather than worrying about hp versus bhp.

Horsepower vs torque?

Engines are often described using two key figures: torque and horsepower. Torque is the engine’s turning force, while horsepower describes how much of that force is delivered over time as the engine spins faster.

A simple gym analogy is that torque is like a powerlifter – focused on raw strength – while horsepower is like an endurance athlete, able to sustain effort at speed. The two are linked, since horsepower is calculated from torque and engine speed (RPM).

Torque is measured in Newton metres (Nm) or foot-pounds (ft/lb), and horsepower in hp or kW.

In general, diesel engines produce more low-end torque, making them strong for towing and carrying loads, while petrol engines tend to produce more horsepower by revving higher, which helps with acceleration and top speed.

How is horsepower measured?

You may have heard the idea that one horsepower equals the power of one horse – and that’s partly true, just not in a literal sense.

Horsepower was introduced in the late 1760s by steam engine pioneer James Watt, who needed a way to compare his engines to the horses they were replacing.

He defined one horsepower as the ability to do 33,000 foot-pounds of work per minute – roughly the amount of work a horse could sustain over time. It was a practical way to help customers understand how powerful his steam engines were.

Today, no one measures cars by putting them next to horses. Instead, power is measured using a device called a dynamometer (or “dyno”), which calculates an engine’s output under controlled conditions.

What horsepower is my car?

To find out what horsepower your car has, you can usually check it in a few simple ways:

• The quickest option is to look it up online using your registration number (in the UK), or check your owner’s manual or the manufacturer’s website. These will give you factory-rated horsepower (often shown as BHP in the UK).
• If you want a more precise, real-world figure, a garage can run a dyno (dynamometer) test to measure power at the wheels, or you can use an OBD-II device with a performance app to estimate it.

How does horsepower impact a car’s performance?

As a general rule, more horsepower means a car can accelerate faster and achieve higher speeds.

A simple way to picture this is to imagine pushing a car yourself. If a friend helps you push, there’s more force behind it, so the car moves off more quickly and with greater ease.

It’s not quite that straightforward in reality. For example, doubling a car’s power from 100hp to 200hp won’t make it twice as fast. Other factors such as weight, tyre grip, and aerodynamics all play a major role.

At higher speeds, aerodynamics become increasingly important, often limiting how fast a car can ultimately go regardless of horsepower.

Why you should consider horsepower when buying a car

Horsepower matters because it directly affects how your car feels and performs in everyday driving. Lower-powered cars (around 75hp, for example) are usually fine for city driving, but they can feel slow when you need to accelerate. Higher-powered cars (500hp+) deliver much stronger, quicker acceleration, which makes driving more effortless.

Weight also plays a big role. For instance, heavier cars need more power to move, which is why small city cars tend to have modest engines, while larger SUVs are typically more powerful.

If you drive on motorways often, more horsepower can make a noticeable difference. It helps you join fast-moving traffic more confidently, overtake more easily, and accelerate without having to push the engine hard or drop multiple gears.

For towing, power is also important because extra weight demands more from the engine. In these cases, torque is just as crucial as horsepower, which is why many towing-focused drivers prefer diesel engines.

In short, the right amount of horsepower helps ensure your car suits how and where you drive – whether that’s city streets, motorways, or towing heavy loads.

Horsepower FAQs

Does one horsepower equal one horse?

No, one horsepower doesn’t literally equal the power of one horse. It’s a unit created by James Watt to compare engine power to a horse’s work output in a specific context.

How much horsepower is good?

There’s no single “good” horsepower figure: it depends on the car and what you want from it. A car’s weight, grip, aerodynamics, and intended use all play a big role in how powerful it feels and performs.

What car has the most horsepower?

The car with the most horsepower (in a claimed production-intent model) is the Devel Sixteen, which is said to produce over 5,000hp from its massive V16 engine.

Other ultra-powerful hypercars include the Koenigsegg Gemera with around 2,300hp, and the Rimac Nevera, an electric hypercar producing about 1,900hp.

Can I increase the horsepower of my car?

Yes, you can increase your car’s horsepower, but it usually involves modifying the engine.

The most common method is an engine control unit (ECU) remap, often called “chipping”, where the car’s software is adjusted to alter things like fuel delivery, ignition timing, and turbo boost to produce more power.

However, there are trade-offs. Increasing horsepower can put extra strain on the engine, may void your manufacturer warranty, and could increase your insurance costs.

How much horsepower does a ‘normal’ car have?

There’s no single answer, because it depends on the type of car. But broadly speaking, a typical city car might have around 70-100hp, a family hatchback around 120-160hp, and a supercar 500hp or more. Anything under 100hp can feel a bit underpowered once you’re out of town or on the motorway.

Do electric cars have horsepower?

Yes, electric cars do have horsepower. Their electric motors produce power that’s measured in the same way as petrol and diesel engines.

The difference is how that power is delivered: EVs can reach maximum output instantly, while petrol and diesel engines usually need to build up revs to hit their peak performance.

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