Power Converter — watts, kilowatts, horsepower & more

How it works

Power is the rate of energy use — one watt is one joule per second. Every unit is a fixed multiple of the watt (NIST SP 811):

• 1 horsepower ≈ 745.70 W — the mechanical (550 ft·lbf/s) horsepower used for engines, so 1 hp ≈ 0.7457 kW.
• 1 metric horsepower (PS) = 735.49875 W, a little less than the mechanical hp — common on European car specs.
• 1 kilowatt = 1,000 W and 1 megawatt = 1,000,000 W.
• 1 BTU per hour ≈ 0.293 W, used for heating and air-conditioning ratings.

The calculator converts your value to watts and then to the unit you want, so any pairing works the same way.

Worked example

Converting 1 horsepower to kilowatts: 1 hp = 745.70 W = 0.7457 kW. Going the other way, 1 kilowatt = 1,000 W ≈ 1.3410 hp, and 1 hp ≈ 1.0139 metric horsepower.

Frequently asked questions

How many watts are in one horsepower?

About 745.7. This is the mechanical horsepower (550 foot-pounds-force per second), so a 200 hp engine produces about 149 kW.

What is the difference between hp and metric horsepower (PS)?

Mechanical horsepower is 745.70 W; metric horsepower (PS, or CV) is 735.50 W. So one metric horsepower is about 98.6% of a mechanical one — the two differ by roughly 1.4%.

How do I convert kilowatts to horsepower?

Multiply kilowatts by about 1.341, since 1 kW ≈ 1.341 hp. For example, a 100 kW motor is about 134 hp.

What is a watt?

The SI unit of power — one joule of energy per second. A one-watt device uses one joule each second; a 60-watt bulb uses 60 joules per second.

What does BTU per hour measure?

It rates heating and cooling power. One BTU per hour ≈ 0.293 W, so a 12,000 BTU/h air conditioner is about 3,517 W (3.5 kW).

Is power the same as energy?

No. Energy is the total amount of work (measured in joules or kWh); power is how fast that energy is delivered (joules per second, i.e. watts). Power × time = energy.