Convert between watts, kilowatts, horsepower, BTU/h and more — instant results across all power units.
Power is the rate at which energy is transferred or consumed. It is expressed in many different units depending on the field of application — watts in electrical engineering, horsepower in automotive and mechanical contexts, BTU/h in heating and air-conditioning, and ergs per second in physics. Converting between these units is essential when comparing specifications, performing engineering calculations, or verifying equipment ratings.
This tool converts between all common power units in real time. Simply type a value and choose the source unit; every other unit updates instantly. The SI prefix family (picowatt through petawatt) covers applications from semiconductor signal levels up to the total output of the largest power stations on Earth.
All conversions use the watt as an intermediate base unit. To convert from one unit to another, multiply the source value by its watt-equivalent factor, then divide by the target unit's watt-equivalent factor:
Here f denotes the conversion factor (in watts) for each unit. For example, 1 mechanical horsepower equals 745.69987 W, while 1 BTU/h equals 0.29307107 W.
SI Prefixes
Horsepower Variants
Thermal & Mechanical
A traditional 60 W incandescent bulb produces the same light output as a modern 9 W LED — the LED is roughly 85 % more efficient. At 9 W, the LED draws about 30.7 BTU/h and consumes just 9,000 mW.
A typical 1.5-litre petrol engine fitted to a UK family hatchback develops around 130 hp(l) (mechanical horsepower), which is approximately 96.9 kW or 96,900 W. Expressed in metric horsepower, the same engine produces about 131.7 hp(M).
A modern laptop CPU operates within a thermal design power (TDP) of 15–45 W, while a smartphone processor typically dissipates 3–8 W. In contrast, discrete graphics cards for gaming can draw between 150 W and 450 W under full load.
A large offshore wind turbine installed around the UK coast has a rated capacity of 12–15 MW. At maximum output, a single 15 MW turbine generates 15,000 kW — enough to power approximately 15,000 average UK homes simultaneously.
Enter any numeric value in the input field at the top of the calculator.
Select the unit you are converting from in the drop-down list. All 19 units — SI prefix series, horsepower variants and thermal/mechanical units — are available.
The converter immediately multiplies your value by the chosen unit's watt-equivalent factor to obtain the intermediate value in watts.
It then divides the watt value by each target unit's factor to populate all result cards simultaneously.
Results are grouped: SI units (pW → PW) are always visible; horsepower variants and other units are in collapsible sections that you can expand as needed.
Always verify which horsepower definition applies to your context — mechanical hp(l), metric hp(M) and electric hp(E) differ by up to 1.4 %, which matters for engineering tolerances.
When comparing heating and cooling equipment, BTU/h is the standard for Anglo-American markets, whereas continental Europe and Asia typically use kW or kcal/h.
Tons of refrigeration (TR) is a unit specific to air-conditioning and refrigeration. One TR equals 3,516.85 W or approximately 12,000 BTU/h.
For very small signals — semiconductor sensors, radio receivers, audio amplifiers — use microwatts (µW) or nanowatts (nW) to keep figures readable.
When working with electricity bills, note that power (watts) differs from energy (watt-hours). A 1 kW appliance running for 1 hour consumes 1 kWh of energy.
The watt (W) is the SI unit of power, defined as one joule per second (J/s). It was named after Scottish engineer James Watt and was formally adopted by the International System of Units. All other units in this converter can be expressed as exact or approximate multiples of the watt.
The answer depends on the definition. Mechanical (imperial) horsepower equals 745.69987 W; metric horsepower equals 735.49875 W; and electric horsepower equals exactly 746 W. When comparing engine specifications, always note which definition is used — American and British standards generally use mechanical hp, while European manufacturers historically used metric hp.
A kilowatt (kW) is a unit of power — the rate of energy use at any given moment. A kilowatt-hour (kWh) is a unit of energy — the total amount of energy consumed over a period of time. Specifically, 1 kWh is the energy used by a 1 kW device running for one hour. Electricity bills measure energy in kWh, not power in kW.
BTU/h stands for British Thermal Units per hour. It is the rate of heat transfer corresponding to one BTU of thermal energy per hour, where 1 BTU equals the energy required to raise one pound of water by 1 °F. It is used extensively in the United States and the United Kingdom for rating heating, ventilation and air-conditioning (HVAC) equipment. 1 BTU/h ≈ 0.293 W.
A ton of refrigeration (TR) is a unit of cooling power widely used in HVAC engineering. It originates from the latent heat required to melt one short ton (2,000 lb) of ice in 24 hours. One TR equals 12,000 BTU/h or approximately 3,516.85 W. Air-conditioning units in the United States are commonly rated in tons (e.g. a 3-ton unit delivers 3 TR of cooling).
Horsepower was originally defined to describe mechanical work — specifically the sustained output of a draft horse. Electronic and computing devices are rated in watts because power consumption in electronics is inherently electrical, and watts is the SI unit that directly relates voltage, current and power. Converting a GPU's TDP to horsepower is mathematically possible but not conventionally meaningful in electronics engineering.
All conversion factors are based on internationally accepted standards. Mechanical horsepower uses the SAE definition (550 ft·lbf/s = 745.69987 W). Results are for informational purposes; always verify critical values with authoritative references.