Power Converter – Watts to Horsepower, kW & BTU

This free power converter turns any power measurement into the unit you need. It handles watts to horsepower, kilowatts, BTU per hour, megawatts and more. Power is the rate at which a device uses or produces energy. Different industries measure it in different units. Electricians work in watts and kilowatts. Engine makers quote horsepower. Manufacturers rate air conditioning in BTU per hour. Type a value into the calculator above, and this power unit converter returns an instant, accurate result for every common power unit. There is no signup and no limit.

Below you will find the exact formulas, worked examples and reference tables for every conversion the tool performs. Use them to check the math by hand or to learn how each unit relates to the others.

What Is Power and How Is It Measured?

Power is the amount of energy a system transfers or converts per unit of time. The SI unit of power is the watt (W), which equals one joule per second. In other words, a device rated at one watt uses one joule of energy every second it runs. The watt is an internationally standardized SI unit, so it anchors every other power unit. The unit takes its name from James Watt. His work on steam engines made measurable power output central to modern engineering.

Electrical power uses metric prefixes built on the watt. A kilowatt is 1,000 watts. A megawatt is one million watts. A gigawatt is one billion watts. Engines and motors traditionally use horsepower for mechanical power. Furnaces and air conditioners usually use BTU per hour for thermal and cooling power. This page explains how to move between all of these systems. For the formal definition of the watt, the United States National Institute of Standards and Technology (NIST) maintains the official measurement standards.

These units describe real consumption. According to the US Energy Information Administration, the average American home used about 10,500 kWh of electricity in 2022, or roughly 877 kWh each month. The US Department of Energy also reports that electric motors consume nearly 70% of all industrial electricity. Lighting accounts for roughly 15% of a typical home's power use. Numbers like these only make sense once you can convert freely between watts, kilowatts and horsepower.

How to Convert Watts to Horsepower

To convert watts to horsepower, divide the wattage by the number of watts in one horsepower. Three slightly different definitions of horsepower exist, so the divisor depends on which one you need:

• Mechanical (imperial) horsepower: HP = watts / 745.7. The United States uses this standard for engines and motors.
• Electrical horsepower: HP = watts / 746. Engineers apply this when they rate electric motors.
• Metric horsepower (PS): HP = watts / 735.5. Europe uses this for car engines.

For most everyday work, use mechanical horsepower. For example, a 2,000 watt electric motor produces 2,000 / 745.7 = 2.68 mechanical horsepower. The reverse calculation multiplies by 745.7. So 1 hp to watts gives 745.7 W, and 2 hp to watts gives 1,491.4 W. This also answers how many watts in a horsepower: about 745.7 watts for mechanical horsepower. Master this single relationship, and you can read any engine, pump or motor specification with confidence.

Watts to Horsepower Conversion Table

This table uses mechanical horsepower (divide by 745.7) for quick reference across common wattages.

How to Convert kW to HP and Kilowatts to Horsepower

Converting kw to hp is one of the most common power conversions. You use it whenever you compare an electric motor rated in kilowatts to an engine rated in horsepower. One kilowatt equals 1,000 watts. So the formula for kilowatts to horsepower is HP = kW x 1.341, using mechanical horsepower. That means 1 kw to hp gives 1.341 hp, and a 100 kW motor equals 134.1 hp. For this single conversion, our dedicated kW to HP converter gives an instant answer.

The reverse direction, hp to kw, multiplies horsepower by 0.7457. One horsepower therefore equals 0.7457 kW, and a 200 hp engine equals 149.1 kW. Run the reverse on the HP to kW converter, or follow a worked example on the convert HP to kW page. The table below covers the range you meet most often in vehicle, pump and generator specifications.

How to Convert Watts to Kilowatts and Kilowatts to Watts

The conversion between watts to kilowatts is the simplest on this page. Both are SI units in the same decimal system. To go from watts to kilowatts, divide by 1,000. To go from kilowatts to watts, multiply by 1,000. So a 1,500 watt hair dryer draws 1.5 kW, and a 2 kW space heater draws 2,000 W. This answers how many watts in a kilowatt: exactly 1,000 watts. For that exact conversion, see the kilowatts to watts converter. Your electricity bill measures energy in kilowatt-hours (kWh). One kWh is a kilowatt of power sustained for one hour.

Watts, Kilowatts and Your Electricity Bill

Understanding power conversion pays off when you read your electricity bill. The utility charges you for energy in kilowatt-hours. That figure combines the power a device draws, in kilowatts, with how long it runs, in hours. To estimate the running cost of any appliance, follow three steps. First, convert its rating to kilowatts. Second, multiply by the hours of use. Third, multiply by your per-kilowatt-hour rate.

Here is a worked example. A 1,500 watt space heater is 1.5 kW. Run it for 5 hours and it consumes 7.5 kWh. At a rate of 15 cents per kWh, that costs about 1.13 dollars per day. Do this for your biggest appliances, such as air conditioners, water heaters and electric ranges. The exercise quickly shows where your energy budget actually goes. To convert between joules, calories and kilowatt-hours, use the energy conversion calculator.

How to Convert BTU to Watts and Watts to BTU

Heating and cooling equipment in North America carries a BTU per hour rating, while the rest of the world uses watts. So converting btu to watts matters when you compare air conditioners, heaters and furnaces. One watt equals 3.412 BTU per hour. That figure answers the common question of how many btu in a watt. To convert BTU per hour to watts, divide by 3.412. To go the other way, watts to btu, multiply the wattage by 3.412.

For example, a 10,000 BTU air conditioner draws 10,000 / 3.412 = 2,931 watts of electrical power. The section below gives exact figures for the two most searched cooling ratings.

12000 BTU to Watts and 5000 BTU to Watts

The figure 12000 btu to watts equals 3,517 watts, or about 3.5 kW. That is the standard rating for a one ton air conditioner. It cools a room of roughly 450 to 550 square feet and usually needs a dedicated 15 or 20 amp circuit. The smaller 5000 btu to watts equals 1,465 watts, or about 1.47 kW. A compact window unit at that rating cools a single small bedroom. To convert cooling capacity between BTU and tons of refrigeration, use the BTU to tons converter. The table summarizes the most common BTU ratings and their wattage.

5 HP to kW, 2 HP to Watts, and 750 Watts to HP

Small motor ratings come up constantly in pumps, fans and power tools, so here are the exact values. The conversion 5 hp to kw equals 3.73 kW, because 5 x 0.7457 = 3.73. The conversion 2 hp to watts equals 1,491 watts, since 2 x 745.7 = 1,491. And 750 watts to hp equals 1.006 hp. That close match is why sellers often label a 750 W motor as a one horsepower unit. These small conversions show how closely 746 watts and one horsepower align in everyday equipment.

How to Convert Watts to Amps (100 Watts to Amps)

People often want to convert watts to amps to size wiring, breakers and fuses. Power and current are not the same thing, so you also need the voltage. The relationship is amps = watts / volts. The same wattage draws very different current depending on the circuit voltage. For instance, 100 watts to amps on a standard 120 volt household circuit is 100 / 120 = 0.83 amps. The same 100 watts on a 12 volt car circuit is 100 / 12 = 8.33 amps. Because the answer depends on voltage, the converter above handles pure power units. You apply the voltage separately when you size electrical circuits.

Megawatts, Gigawatts and Large-Scale Power

When you move from home appliances to power plants and the electrical grid, the units scale up quickly. One megawatt equals 1,000 kilowatts. So converting megawatts to kilowatts means multiplying by 1,000. Going further, megawatts to watts multiplies by one million. That answers the question of how many watts in a megawatt: exactly 1,000,000 watts. At the largest scale, gigawatts to megawatts multiplies by 1,000, since one gigawatt equals 1,000 megawatts or one billion watts.

These units describe real infrastructure. A single large wind turbine produces between 5 and 15 megawatts. A typical nuclear reactor generates about 1,000 megawatts, which equals one gigawatt. Engineers discuss national grids in tens of gigawatts. The table puts the full ladder of power units in one place.

kVA, kW and Apparent Power

In electrical engineering you will meet the kilovolt-ampere (kVA), a unit of apparent power, alongside the kilowatt of real power. Converting kva to kw requires the power factor. The power factor is a number between 0 and 1 that describes how efficiently current does useful work: kW = kVA x power factor. The reverse, kw to kva, divides kilowatts by the power factor. At a typical power factor of 0.8, a 100 kVA generator delivers 80 kW of real power. The same logic applies to watts to kva at smaller scales. Generator and transformer nameplates list kVA rather than kW because the apparent power tells you the current the equipment must carry.

Real-World Power Examples

Putting numbers to familiar objects makes these conversions intuitive. The following examples show power output across everyday and industrial equipment. Each value matches the formulas above.

• LED light bulb: 10 W, equal to 0.013 hp. A modern LED replaces a 60 W incandescent bulb while using a fraction of the power.
• Microwave oven: 1,000 W, equal to 1 kW or 1.34 hp. That high draw is why microwaves often need their own circuit.
• Hair dryer: 1,500 W, equal to 1.5 kW or 2.01 hp, one of the highest draws among handheld appliances.
• One ton air conditioner: 12,000 BTU per hour, equal to 3,517 W or 3.52 kW.
• Electric car motor: 150 kW, equal to about 201 hp, comparable to a mid size gasoline engine.
• Wind turbine: 3 megawatts, equal to 3,000 kW or about 4,023 hp, enough to power roughly 1,500 homes.

Power Unit Conversion Reference

This power unit converter supports the full range of units in the reference table below. Each factor sits relative to the watt, the SI base for power, so you can confirm any result the calculator produces.

The History and Three Definitions of Horsepower

Horsepower causes the most confusion in power conversion, so it helps to know where it came from. In the late 1700s, James Watt needed a way to sell his steam engines to mine owners. Those buyers measured work by the number of horses they replaced. Watt measured a horse turning a mill wheel. He settled on a figure that became one mechanical horsepower, roughly 745.7 watts. The unit stuck so well that it still rates car engines, tractors and pumps more than two centuries later.

Over time three definitions emerged. Mechanical horsepower (745.7 W) is the imperial standard for engines in the United States. Metric horsepower, written as PS or CV in Europe, equals 735.5 watts. It appears on most European car brochures, which is why one engine can carry two slightly different horsepower figures. Electric motor makers reserve electrical horsepower (746 W) for their products. The gap between the three stays under two percent. Still, it matters when you match a motor to a load, so always check which definition a specification uses.

Why Power Factor Matters for kVA and kW

Power factor is the hidden variable that trips up many electrical conversions. In a perfect direct current circuit, watts and volt-amperes match exactly, so kW and kVA would be the same. Alternating current systems behave differently. Motors, transformers and fluorescent lighting draw current that falls partly out of step with the voltage. That out-of-step current does no useful work, yet the wiring still has to carry it.

The power factor, a value from 0 to 1, captures this gap. A purely resistive load like a heater runs near 1, so its kVA and kW stay almost equal. An inductive load like a large motor might run at 0.8. In that case a 100 kVA supply delivers only 80 kW of real, usable power. This gap explains why utilities bill industrial customers on kVA and why generator nameplates quote both figures. When you convert kVA to kW or watts to kVA, the power factor is the entire conversion.

Choosing the Right Power Unit for Your Project

Selecting the correct unit before you convert saves errors later. For household appliances, lighting and small electronics, stay in watts and kilowatts. That is how nameplates and electricity bills read. For engines, motors, pumps and vehicles, horsepower remains the common language, especially in the United States. Convert your watts to horsepower when you compare against an engine spec.

For heating, ventilation and air conditioning, BTU per hour is the North American standard. A contractor sizing a unit quotes BTU even though the electrical draw stays in watts. For power generation, transmission and large solar or wind installations, megawatts and gigawatts are the working units. Match your unit to the industry, and your numbers stay readable to the people you work with.

How to Use the Power Converter

Using the calculator at the top of this page takes three steps. First, choose the unit you are converting from, such as watts, kilowatts, horsepower or BTU per hour. Second, enter your value. Third, read the result in every other unit instantly. The tool helps students checking physics homework, engineers sizing equipment, HVAC installers comparing air conditioners, and homeowners reading an appliance label. It runs entirely in your browser, so there is no waiting, no signup and no limit on conversions.

Common Mistakes When Converting Power Units

A few errors come up again and again. The most frequent one confuses power with energy. Watts measure the rate of energy use, while watt-hours and kilowatt-hours measure total energy over time. So a 1,000 watt appliance running for two hours uses 2 kWh of energy, not 2,000 watts. Another common slip mixes the three horsepower definitions and lands a result that is off by one or two percent. A third tries to convert watts to amps without a voltage, which is mathematically impossible. Finally, people often treat an air conditioner's BTU rating as its electrical draw, when the BTU figure describes heat moved, not power consumed.

Limitations of Power Conversion

Power conversions stay exact for mechanical and thermal units, but a few cautions apply. First, the three horsepower definitions differ by up to one and a half percent. Always confirm whether a specification uses mechanical, electrical or metric horsepower before you convert. Second, you cannot turn watts into amps without the voltage, and you cannot turn kVA into kW without the power factor. Third, BTU figures on appliances sometimes describe cooling capacity rather than electrical input. A 12,000 BTU air conditioner removes 3,517 watts of heat but may draw less electrical power, depending on its efficiency rating. When precision matters for electrical safety or equipment sizing, treat these results as a starting point and check the manufacturer nameplate.