Watt Converter
Convert watts, horsepower, kilowatts, megawatts, BTU per hour, and other power units with fast factor-based calculations.
Enter a power value, choose the source unit, choose the target unit, and calculate the converted result instantly.
Watt Converter
Convert watts, horsepower, kilowatts, megawatts, BTU per hour, and other power units with fast factor-based calculations.
About Watt Conversion
Power unit conversion is all about expressing the same rate of energy transfer in different measurement systems. The watt is the SI unit of power and equals one joule per second. Because it belongs to the metric system and appears throughout electrical engineering, physics, HVAC, and industrial specifications, it makes an ideal reference unit. A watt converter works by translating the source value into watts first, then dividing by the factor for the target unit. Once the factors are defined, any conversion between two supported units becomes a straightforward ratio problem.
Many of the units on this page come from very different technical traditions. Kilowatts and megawatts are metric multiples of the watt and are common in electrical supply, motors, and utility-scale generation. Milliwatts are used in electronics, sensors, optical devices, and low-power signaling. Mechanical and metric horsepower come from older engineering practice and are still widely used for engines, pumps, compressors, and industrial equipment. BTU per hour appears in heating and cooling, especially in HVAC sizing. Calories per second and ergs per second are less common today but still appear in older scientific references or niche contexts. Foot-pound per minute belongs to the imperial mechanical tradition and is useful when comparing older machine specifications.
The converter uses fixed factors to watts for each unit. One kilowatt is exactly 1,000 watts, one megawatt is 1,000,000 watts, and one milliwatt is 0.001 watt. Mechanical horsepower is approximately 745.69987 watts, while metric horsepower is approximately 735.49875 watts. BTU per hour converts at 0.29307107 watts, calorie per second at 4.1868 watts, erg per second at 1×10^-7 watts, and foot-pound per minute at 0.022597 watts. Because every conversion routes through watts, the result remains consistent no matter which starting and ending units you choose.
This matters in real work because equipment data sheets rarely agree on unit conventions. An electrical appliance may be rated in watts, a motor in horsepower, an HVAC unit in BTU per hour, and a power station in megawatts. If you need to compare them, estimate equivalent capacity, or move data from one report format to another, the first step is almost always unit conversion. Students also encounter these conversions in physics and thermodynamics problems where multiple traditions meet in a single question. Converting carefully prevents order-of-magnitude mistakes that can distort a design decision or exam answer.
A good mental check helps. If you convert from kilowatts to watts, the number should get larger because a kilowatt is a larger unit. If you convert from watts to horsepower, the number should usually get smaller because one horsepower is several hundred watts. This converter keeps the process transparent by also showing the equivalent watt value, making it easy to verify that the answer scales in the expected direction. Whether you are comparing engines, checking appliance ratings, or translating an old engineering table, the watt converter provides a quick and consistent bridge across power units.
Examples
These examples highlight the most common power conversions across electrical, mechanical, and thermal contexts.
| Input | Output | Notes |
|---|---|---|
| 1 kilowatt (kW) | 1000 watt (W) | Metric power multiples are exact, so one kilowatt always equals one thousand watts. |
| 1 horsepower (mechanical) (hp) | 745.69987 watt (W) | Mechanical horsepower is common for engines and motors, especially in North American equipment data. |
| 1000 watt (W) | 1.34102 horsepower (mechanical) (hp) | Converting back from watts to horsepower is useful when comparing electrical loads to motor or engine ratings. |
| 500 watt (W) | 0.5 kilowatt (kW) | Converting between watts and kilowatts is common in appliance energy labels and small-equipment specs. |
How to Use
- Enter the numeric power value you want to convert. The calculator accepts whole numbers or decimals.
- Choose the source unit from the From Unit list and the destination unit from the To Unit list.
- Click Calculate to see the converted value and the equivalent power expressed in watts.
- Use the worked examples to compare common kilowatt, horsepower, and watt conversions, then reset the form for a new case.
Frequently Asked Questions
Why does the converter use watts as the middle step?
Watts are the SI base unit for power and provide a neutral reference across electrical, thermal, and mechanical systems. Converting everything to watts first ensures each pairwise conversion stays consistent and easy to verify.
What is the difference between mechanical and metric horsepower?
They are two closely related but distinct historical definitions of horsepower. Mechanical horsepower is about 745.69987 watts, while metric horsepower is about 735.49875 watts, so the numerical difference is small but real.
When should I use BTU per hour instead of watts?
BTU per hour is common in heating and cooling specifications, especially for HVAC capacity. Watts are more universal in physics and electrical work, so converting between the two helps compare thermal and electrical equipment on the same basis.
Why can the converted number get larger even though the power is the same?
The physical power does not change, only the size of the unit you are using to describe it. Converting into a smaller unit produces a larger numerical value, while converting into a larger unit produces a smaller numerical value.
Are these factors accurate enough for engineering work?
Yes, the listed factors are appropriate for general engineering, education, and specification comparisons. For contractual or regulatory documents, you should still use the exact unit convention required by the governing standard.