Kw, bhp, PS: All The Mechanical Measurements Explained

One of the most important parameters that most car buyers check for while shortlisting a car for purchase is Power. This Power is directly related to the on-road performance of a car; this means the more powerful a car is, the more robust would be its on-road performance. Generally, the car's Power is measured in terms of BHP as it provides an easy basis for comparing the performance of different cars. 

What is BHP?

BHP is considered a more realistic measurement of Power since it considers the loss of Power due to friction. The full form of BHP is brake-horsepower which is very commonly used in the United Kingdom. The formula to calculate BHP is:

BHP = (Torque X BPM)/5252

As the energy loss is taken into consideration while calculating, the value of BHP is generally lower than HP. In simple words, the higher is the BHP, the higher will be the top speed of the car.

Another unit of Power that is commonly used alongside BHP happens to be WHP or wheel-horsepower. Again, this considers torque to determine the Power generated by the engine!

What is HP?

Some consider HP to be a completely made-up power measurement. Since HP doesn't consider energy loss, the value is hypothetical in a way.

The formula to calculate HP is:

HP = (F X d)/t

Where F=force in pounds, d=distance in feet, t=time in minutes

This unit of Power was invented by Mr. James Watt (also known as the master of the steam engine). One of the most common misconceptions about horsepower is that it is equal to the Power of a horse; that is not quite true. Horsepower is very important when you're talking about a car's performance, as more horsepower translates into more speed.

What is kW?

We know that the SI unit of Power is a Watt. When we're trying to define higher power values, like in a car, we need higher units of Power. Kilowatts is one such unit. 1 kW is equal to 100 watts. kW is generally used in the Southern Hemisphere to define the Power generated by cars.

The formula to calculate kW is the simple Power calculating formula:

Q(kW) = (Peak Torque (Nm) X RPM)/9565

If we're comparing kilowatts to other notations of power, then we find that,

• 1 kW = 1.34102 Horsepower or 1 HP = 0.7457 kilowatt
• 1 kW = 1.34 BHP or 1 BHP = 0.7462 kilowatt
• 1 kW = 1.35962 PS or 1 PS = 0.7354 kilowatt

What is PS?

PS is also known as the "metric horsepower." It is most commonly used in Germany and various parts of Europe. PS is actually short for Pferdestärke.

The formula to calculate PS is very similar to BHP. For perspective, 1 PS equals 98.6% of Horsepower (HP). Since there is just a minor difference between PS and HP, either work during presentations. Except for the UK, entire Europe follows this system.

Now that all the fundamentals regarding the calculation and importance of Power are clear to you, you can make an informed decision while comparing different cars.