Power Converter: Units, Formulas, and Examples
Convert watts, kilowatts, mechanical horsepower, metric horsepower, and heat-output rates.
How to convert power
Converted value = input value × source factor ÷ target factor. Factors express each unit in watts.
Keep the source and target definitions consistent, apply the conversion to the original value, and round the final answer to the precision needed for your calculation.
Understanding power units
Power measures the rate of energy transfer. One watt equals one joule per second. Mechanical horsepower and metric horsepower use different definitions; the labels identify which is being used. BTU uses the International Table definition.
| Unit | In W |
|---|---|
| Watts (W) | 1 |
| Kilowatts (kW) | 1,000 |
| Megawatts (MW) | 1,000,000 |
| Gigawatts (GW) | 1,000,000,000 |
| Mechanical horsepower (hp) | 745.699871582 |
| Metric horsepower (PS) | 735.49875 |
| BTU IT per hour (BTU IT/h) | 0.293071070172 |
| Thermochemical kcal per hour (kcal/h) | 1.16222222222 |
Worked power examples
1 kilowatt = 1,000 watts, approximately 1.3410220896 mechanical horsepower. 1 metric horsepower = 735.49875 watts.
Frequently asked questions
Which definitions should I use?
Kilowatts and kilowatt-hours measure different quantities. Multiply power by a time interval to obtain energy.
Why do displayed results sometimes differ slightly?
Intermediate arithmetic uses browser floating-point numbers. Display rounding and the precision of an original measurement can affect the last digits. The unit conversion does not improve the accuracy of a measured value.
Does converting back recover the original value?
Using the unrounded result normally recovers the original quantity within floating-point precision. Copying a rounded number can introduce a small difference.
How are the unit definitions documented?
For physical unit definitions and conversion factors, see the NIST conversion reference.