Power Calculator

1. Enter any two of power, work and time.
2. Leave the one you want to find blank.
3. Read the result.
4. See which value was solved for and the formula used.

Here is what each result means:

Power is how fast work is done or energy is used. It equals the work divided by the time, so doing the same job in less time takes more power. A powerful motor does a lot of work quickly, while a weak one takes longer for the same task.

In SI units, power is measured in watts, where one watt is one joule per second. Power comes up everywhere, from light bulbs and engines to the human body. It tells you the rate of energy use, not the total, which is why a short burst of high power can use the same energy as a long stretch of low power. This calculator links power, work and time.

This is why two engines can do the same job yet feel very different. A powerful engine finishes the work quickly, while a weaker one takes longer to move the same energy. The total work can be identical; what sets them apart is the rate, and that rate is exactly what power measures.

It rearranges one relation to solve for whichever value you leave blank.

1. For power, divide the work by the time.
2. For work, multiply power by time.
3. For time, divide the work by the power.

The work in the formula is energy transferred; the work calculator finds it from force and distance.

A machine does 1000 joules of work in 5 seconds.

Calculation: P = W / t = 1000 / 5 = 200 watts. To do the same 1000 joules in half the time, 2.5 seconds, would take twice the power, 400 watts.

One relation, rearranged for whatever you need to find.

All three come from P equals W over t, so any two of the values give the third.

These are closely linked but distinct.

Power is a rate, so the same energy can be delivered at high power quickly or low power slowly.

The Amount of Work

More work in the same time means more power, in direct proportion.

The Time Taken

Doing the same work faster raises the power. Half the time means double the power.

The Task Itself

Harder or heavier tasks need more work, and doing them quickly needs high power.

Physics Homework

Find power, work or time in an energy problem.

Appliances and Motors

Relate a device power rating to the energy it uses over time.

Fitness and Machines

Work out the power output of a person or engine doing a task.

1. Confusing Power and Energy

Power is the rate; energy is the total. A high-power device is not always high-energy if it runs briefly.

2. Forgetting to Divide by Time

Power is work over time, not just the work. The time is essential.

3. Mixed Units

Use joules, seconds and watts for a clean SI result.

4. Zero Time or Power

Solving for power needs a nonzero time, and solving for time needs a nonzero power.

5. Mixing Watts and Watt-hours

Watts measure power; watt-hours measure energy. They are not the same.

The relation is exact; only the displayed decimals are rounded.

Power is how fast work is done or energy is used. It equals the work divided by the time. Doing the same work in less time means more power. It is measured in watts.

Divide the work by the time. Doing 1000 joules of work in 5 seconds is a power of 1000 over 5, which is 200 watts.

A watt is the SI unit of power, equal to one joule per second. A 60 watt bulb uses 60 joules of energy every second it is on.

Multiply the power by the time. Leave the work field blank and enter power and time, and the calculator solves for the work done.

Divide the work by the power. Leave the time field blank and enter work and power to solve for how long the task takes.

Energy, or work, is the total amount, in joules. Power is the rate of using it, in watts. A device can be high-power for a short time yet use little total energy.

No. A watt is a unit of power, a rate. A watt-hour is a unit of energy, the amount used by one watt over one hour. Energy equals power times time.

This tool uses power equals work over time. Electrical power from voltage and current is a related but separate formula, power equals voltage times current.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Power (physics) (Wikipedia).
• Power explained (Maths Is Fun).
• Watt (Wikipedia).