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Understanding power is essential for an overall understanding of physics and other scientific disciplines. Our power calculator can help you to accurately solve any power-related problems.

This comprehensive guide to power will teach you everything you need to know about power, including various formulas and examples. If you find this page useful, please share it with your friends.


Why use a power calculator?

A power calculator can make the math portion of solving physics problems a lot easier for you, especially when you're working with difficult concepts like power, energy, and force.

Calculators can save you time and make sure you're using the right numbers as you work through equations and problems.

Physics is a tough subject that deals with difficult concepts ranging from electromagnetism to gravity to subatomic particles. One subject that is relevant for almost all parts of physics is the concept of energy, force, and power.

What is power?

The way we speak about power in everyday life usually refers to strength and energy. This is somewhat related to the actual scientific definition of power, which might make it a bit easier to understand.

Power is defined as the rate at which work is done.

What is "work"?

Work is defined as the energy transferred by a force (where force = mass * acceleration). The formula for work is:

Work = Force * Distance

So it takes energy work on something. This makes sense if you think about how we use the word work in our everyday life. If you have to lift a box for work, you need to exert energy to lift that box and do the work. Make sense?

So back to power. If it takes energy to do work and power is the rate that work is done, power is basically how long it takes to get the work done.

What is the correct formula for power?

The formula for power looks like this:

Power = Force * Velocity

= F * v

Another common formula for power is:

Power = Work / time

= W / t

What's the standard unit of power?

The formula for power typically multiplies force (measured in newtons) by velocity (measured in meter per second). However, watts are the SI unit for power.

The other formula for power will leave you with units of Joules/s (J/s). You divide the amount of work done by the time it takes to do that work. Work is measured in Joules (J) and the standard unit for time is seconds (s).

J/s can also be converted to Watts. 1 Watt is equal to 1 J/s.

The Watt is named after the scientist and inventor James Watt. Watt studied power and energy; he was also responsible for perfecting and improving upon some of the first steam engines that would go on to power factories, farms, and more.

Let's look at a quick example problem that uses some of these relevant formulas.

What's an example of a solved power problem?

Using Force and Velocity

Let's say a braking car exerts a force of 100 Newtons at a velocity of 1 m/s. What is the power exerted by this stopping car?

With this problem, we simply plug the force and the velocity given into the equation for power.

P = F * v

= 100 N * 1 m/s

= 100 J/s = 100 Watts

But, what if we were given the same problem with slightly different numbers and using the second formula for power?

Using Work and Time

Say that instead of force and velocity, we are given force, distance, and time? A car exerts a force of 100 Newtons over 10 seconds for a distance of 10 meters.

First, we need to calculate the work done using the given force (100 Newtons) and the distance traveled (10 meters).

Work = Force * Distance

= 100 Newtons * 10 meters

= 1000 Joules

Next, we divide the work done by the amount of time it took to do that work to get the power.

Power = Work / time

= 1000 Joules / 10 seconds

= 100 J/s = 100 Watts

This is just one example of how you will be expected to use the various formulas concerning energy, force, and work in order to calculate power.

How does horsepower relate to watts?

While the most widely used unit for power is Watts, another common unit used is known as "horsepower" (hp).

1 hp = the power needed to lift 75 kg = 735.5 Watts

For the first horsepower calculations, there was a debate on the force produced by a horse. Engineers eventually agreed that a horse can produce 33,000 foot-pounds per minute.

Types Of Horsepower

Depending on where you were in the world the definition would vary. For example, a mechanical horsepower is approximately 745.7 watts.

Today horsepower has six standardized definitions for different types of power, which are all in use:

  • mechanical horsepower
  • metric horsepower
  • electrical horsepower
  • boiler horsepower
  • hydraulic horsepower
  • air horsepower

Mechanical horsepower is the one we are familiar with when speaking about cars.


Nowadays using horsepower isn't as relevant, but you'll often hear it used in car commercials and you might find it in some physics problems.

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