Power Converter

Power Converter: Convert Between All Power Units

The Power Converter is a free online tool that instantly converts power values between 11 units spanning electrical engineering, mechanical systems, and thermal applications. Whether you need to compare a car engine rated in horsepower to one rated in kilowatts, convert HVAC capacity from BTU/h to tons of refrigeration, translate milliwatts to watts for an electronics design, or compare utility-scale generation figures in megawatts and gigawatts, this tool delivers high-precision results in real time with configurable decimal places.

All conversions are performed client-side using the Watt (W) as the normalized base unit. Enter a value in any supported unit and every other unit updates simultaneously — no button press required. The "Show all unit conversions" option displays a grouped reference table across all four unit categories, making it easy to compare values at a glance.

Supported Power Units

The converter covers 11 units grouped into four practical categories.

SI Units

• Watt (W) — The SI base unit of power, defined as one Joule of energy transferred per second. Named after Scottish engineer James Watt, it is the universal reference point for all power measurements. Every conversion in this tool normalizes through the Watt.
• Kilowatt (kW) — Equal to 1,000 W. The most commonly encountered unit for everyday power applications: household appliances, electric vehicle motors, small generators, and solar panel array outputs are typically quoted in kilowatts.
• Megawatt (MW) — Equal to 1,000,000 W. Used for large-scale power generation and industrial facilities. A single large wind turbine generates 2–5 MW; a coal or gas-fired power plant might produce 500–1,000 MW.
• Gigawatt (GW) — Equal to 1,000,000,000 W. Used to describe the total installed capacity of national electricity grids, large hydroelectric dams, and the aggregate output of major power generation projects. The Three Gorges Dam in China has a capacity of about 22.5 GW.

Electrical Units

• Milliwatt (mW) — Equal to 0.001 W. The standard unit for signal strength in telecommunications (Wi-Fi, cellular, radio), low-power embedded electronics, and laser output power for consumer devices and optical fiber systems.
• Microwatt (µW) — Equal to 0.000001 W. Used in ultra-low-power microelectronics, RFID systems, energy harvesting circuits (ambient vibration, piezoelectric, thermoelectric), and biological sensors where power budgets are measured in microwatts to maximize battery life.

Mechanical Power Units

• Horsepower — mechanical (hp) — Defined as exactly 550 foot-pounds per second, equal to 745.699872 W. Originally introduced by James Watt to compare steam engine output to draft horse capability, mechanical horsepower remains the dominant power unit for vehicle engines, outboard motors, and industrial machinery in North America.
• Metric Horsepower (PS) — Defined as 75 kilogram-force meters per second, equal to 735.49875 W. Denoted PS (from German: Pferdestärke) or cv (from French: cheval-vapeur), metric horsepower is the standard for vehicle ratings in Europe, Japan, South Korea, and much of Asia. It is approximately 1.4% less than mechanical horsepower.
• Foot-pound per second (ft·lb/s) — The rate of doing work at one foot-pound per second, equal to 1.35581795 W. One mechanical horsepower equals exactly 550 ft·lb/s. This unit appears in torque-speed calculations, rotational power analysis, and ballistics.

Thermal Power Units

• BTU per hour (BTU/h) — The rate of heat transfer equal to one British Thermal Unit per hour, approximately 0.293071 W. Widely used in North America to rate heating and cooling equipment: air conditioners, heat pumps, furnaces, boilers, and water heaters. A 12,000 BTU/h unit corresponds to approximately 3.52 kW.
• Ton of Refrigeration (TR) — Defined as the power required to melt one short ton (2,000 lb) of ice at 0 °C in 24 hours, equal to 12,000 BTU/h or approximately 3,516.85 W. Tons of refrigeration are the preferred capacity unit for commercial chillers, large-scale HVAC systems, industrial refrigeration plants, and data center cooling infrastructure.

How Power Conversion Works

Every conversion is normalized through the Watt in two steps. First, the input value is multiplied by the conversion factor of the source unit to obtain the equivalent value in Watts. Then that Watt value is divided by the conversion factor of the target unit to produce the final result. This two-step approach ensures consistent accuracy for any pair of units without requiring a dedicated formula for every combination.

As an example, converting 150 hp to kilowatts:

• 150 hp × 745.699872 W/hp = 111,854.98 W
• 111,854.98 W ÷ 1,000 W/kW = 111.855 kW

For units involving very large or very small conversion factors — such as microwatts (1 µW = 10⁻⁶ W) or gigawatts (1 GW = 10⁹ W) — the tool automatically switches to scientific notation to keep results readable and unambiguous.

Key Power Reference Values

• 1 kW = 1,000 W = 1.341 hp = 1.360 PS = 3,412.14 BTU/h
• 1 hp (mechanical) = 745.70 W = 0.7457 kW = 550 ft·lb/s = 2,544.43 BTU/h
• 1 PS (metric hp) = 735.50 W = 0.7355 kW = 0.9863 hp
• 1 TR = 3,516.85 W = 3.517 kW = 12,000 BTU/h = 4.716 hp
• 1 BTU/h = 0.293071 W = 0.000293 kW = 0.000393 hp
• 1 GW = 1,000 MW = 1,000,000 kW = 1,000,000,000 W

Practical Applications of Power Conversion

Power measurement spans an enormous range of scales and disciplines. Here are common scenarios where unit conversion is essential:

• Automotive and Motor Ratings: Vehicle engine power is expressed in horsepower (hp) in North America and kilowatts (kW) or metric horsepower (PS) in Europe and Asia. A car with 300 hp delivers 223.7 kW or 304.2 PS. When shopping for imported vehicles or comparing specifications across markets, accurate conversion is essential for meaningful comparisons.
• HVAC and Refrigeration Design: HVAC engineers routinely convert between BTU/h, tons of refrigeration, and kilowatts when sizing equipment, comparing products from different markets, or performing energy calculations. A data center requiring 500 kW of cooling needs approximately 142 TR or 1,706,000 BTU/h of refrigeration capacity.
• Electrical Engineering and Electronics: RF power levels are expressed in milliwatts or dBm, while circuit power dissipation is in watts or milliwatts. Converting between mW, W, and kW is a daily task in antenna design, amplifier specification, power supply design, and PCB thermal analysis.
• Renewable Energy and Grid Analysis: Solar panels are rated in watts peak (Wp) while utility-scale solar farms are described in megawatts or gigawatts. Converting between these scales is necessary when aggregating project data, comparing capacity factors, or translating between residential and grid-level energy discussions.
• Industrial Machinery and Pumps: Pump and compressor power is often specified in horsepower or kilowatts depending on the supplier's country. A pump rated at 50 hp from a US manufacturer and a 37 kW pump from a European supplier are essentially the same power output (50 hp = 37.28 kW), which this tool confirms instantly.
• IoT and Low-Power Design: Battery-powered sensors and wireless nodes are designed around microwatt and milliwatt power budgets. Engineers converting between µW, mW, and W when analyzing sleep-mode current consumption, radio transmission bursts, and harvested ambient energy levels need precision at small scales, which this tool provides with up to 10 decimal places.

Tips for Using the Power Converter

• Enable "Show all unit conversions" to display every supported unit at once, grouped by category. This is ideal for quickly comparing values across disciplines — for example, seeing simultaneously how many hp, kW, PS, and BTU/h correspond to a given watt value.
• Increase the decimal places setting when working with microwatt or milliwatt conversions where precision matters. The tool will automatically use scientific notation when the result falls below 0.0001 or exceeds one trillion.
• Use the Swap button to immediately reverse a conversion — for example, checking that a kW-to-hp result is correct by converting back and verifying you recover the original value.
• The conversion history panel records your last 10 conversions during the session. Click any history entry to restore those values as the current input, making it easy to compare multiple related power values.
• When comparing European and North American vehicle ratings, remember that metric horsepower (PS) and mechanical horsepower (hp) are not the same. Enter a value in PS and check the hp row — a 200 PS engine produces approximately 197.3 hp.