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Power Converter
Convert power between watts, kilowatts, horsepower and heating units. Enter a value, choose the unit you have and the one you want, and the other units are listed under the headline result.
The watt and how horsepower is defined
A watt is one joule per second. All the other units on this page are fixed multiples of it, which makes conversion a matter of one multiplication and one division.
- Mechanical (imperial) horsepower: 550 foot-pounds force per second = 745.69987158 W
- Metric horsepower (PS, CV, ch, pk): 75 kilogram-force metres per second = 735.49875 W exactly
- BTU per hour (IT): 1,055.056 J ÷ 3,600 s ≈ 0.29307 W
- Kilocalories per hour: 4,184 J ÷ 3,600 s ≈ 1.16222 W
Electrical horsepower is conventionally rounded to exactly 746 W, and boiler horsepower is a different, much larger unit; neither is included here.
Why the two horsepowers differ
Mechanical and metric horsepower differ by about 1.4%: one mechanical hp is roughly 1.0139 PS. A car described as 150 PS is about 148 mechanical hp, and the same engine is 110.3 kW. Manufacturers in different regions publish different units, so a gap of one or two percent between brochures does not necessarily mean the engines differ.
As quick conversions, kilowatts × 1.341 gives mechanical horsepower, and kilowatts × 1.36 gives metric horsepower. A 100 kW motor is therefore about 134.1 hp or 135.96 PS.
Reading power ratings correctly
| Rating | In kW |
|---|---|
| 12,000 BTU/h (one "ton" of cooling) | about 3.52 |
| 1 mechanical hp | 0.7457 |
| 1 PS | 0.7355 |
| 2 kW kettle | 2 |
Appliance labels often quote peak or input power, and engines have different figures at the crank, at the wheels and at the plug. A converter cannot tell you which one a number means. Check whether a figure is rated, peak, continuous or measured at the wheels before comparing products.
Power versus energy
Power is a rate; energy is the amount delivered. A 2 kW heater has the same rating whether it runs for a minute or a day, but it uses 2 kWh each hour. If you need to convert an amount of energy such as kWh or BTU, use the energy converter. Heating output quoted in BTU per hour belongs here, while the BTU itself is an energy unit.
When sizing equipment, the useful figure is often the output at the point of use. A motor drawing 2 kW of electrical input may deliver less mechanical power because of losses, and a heat pump can deliver more heat than the electrical power it consumes. These effects belong to efficiency and performance ratios, not to unit conversion, so convert the figures first and then compare like with like.
For rough sizing of a room air conditioner, product manuals and local guidance, not a converter, should decide the required capacity.
Worked example
An engine is rated at 100 kilowatts. What is that in mechanical horsepower?
Inputs
| Value | 100 |
|---|---|
| From | Kilowatts (kW) |
| To | Mechanical horsepower (hp) |
Result
100 kW = 134.102209 hp
| Watts (W) | 100,000 |
|---|---|
| Megawatts (MW) | 0.1 |
| Metric horsepower (PS, CV) (PS) | 135.962162 |
| BTU per hour (IT) (BTU/h) | 341,214.1156 |
| Kilocalories per hour (kcal/h) | 86,042.065 |
| Foot-pounds force per second (ft·lbf/s) | 73,756.2149 |
- Factors are exact definitions where one exists; results are shown to about six significant digits.
Accuracy note: Factors use the standard definitions stated on this page. Results are rounded for display; for engineering or legal work use the full-precision factors.
Frequently asked questions
How many watts are in one horsepower?
One mechanical horsepower is 745.69987158 watts. A metric horsepower is 735.49875 watts.
How many horsepower are in a kilowatt?
One kilowatt is about 1.34102 mechanical horsepower, or about 1.35962 metric horsepower.
What is the difference between hp and PS?
PS, CV and ch are metric horsepower, equal to 735.49875 W. The mechanical hp is about 1.4% larger at 745.7 W.
How many BTU per hour is one kilowatt?
About 3,412.14 BTU per hour, found by dividing 1,000 W by 0.29307 W per BTU/h.
Is power the same as energy?
No. Power is energy per unit time. One watt is one joule per second, and a kilowatt-hour is an amount of energy.
Related calculators
More conversion references
For power conversion tables beyond this tool, see PakMath power conversion tables. PakMath is a sister project of Adzita.