Power Converter

How to Use the Power Converter

Enter a power value, select its unit and the unit you want to convert to, and the result updates as you type. Commonly used to convert engine or motor ratings between horsepower and kilowatts, or air conditioner ratings between BTU/hour and watts. Use the swap button to reverse the direction instantly.

Worked Examples

• 1 horsepower to watts: 1 hp = 745.699872 watts exactly, the defined conversion for mechanical horsepower used in motor and engine specs.
• 150 horsepower (typical car engine) to kilowatts: 150 hp = 111.854981 kW, a figure you'll see on European vehicle spec sheets for a US-rated 150 hp engine.
• 1 kilowatt to horsepower: 1 kW = 1.341022 hp, useful for converting a metric-rated generator or motor into the horsepower figure US buyers expect.
• 12,000 BTU/hour (1 "ton" of AC cooling) to watts: 12,000 BTU/h = 3,516.85 watts of cooling capacity, not the electrical power the unit draws from the wall.
• 1,500 watts (a typical microwave) to horsepower: 1,500 W = 2.011533 hp, showing how a small kitchen appliance's power draw compares to a fraction of one horsepower.

Common Power Units Explained

Watts (W) is the SI unit of power, defined as one joule of energy per second. It's the base unit this converter uses internally, and the unit printed on virtually every electrical appliance.

Kilowatts (kW) and megawatts (MW) scale watts up by 1,000 and 1,000,000 respectively, used for larger loads like motors, generators, and power plants where a plain watt figure would be unwieldy.

Horsepower (hp) is the traditional unit for engine and motor output in the US and a handful of other countries, standardized at exactly 745.699872 watts for mechanical horsepower (note that electrical and metric horsepower definitions differ very slightly, this tool uses the mechanical definition, the most common one for vehicles).

BTU per hour (BTU/h) measures heating or cooling power, mainly for air conditioners, furnaces, and boilers. It's a thermal energy unit repurposed as a rate, and converts to watts at a factor of about 0.293071.

Common Mistakes When Converting Power

A frequent mix-up is treating an air conditioner's BTU/hour cooling capacity as the same number as its electrical power draw. A 12,000 BTU/h ("1 ton") unit delivers about 3,517 watts of cooling, but typically only draws around 1,000 to 1,500 watts of actual electricity, since air conditioners move heat rather than generate it, achieving more cooling output than electrical input. Don't use this converter's BTU/h-to-watts result as an electricity bill estimate.

Another common error is confusing horsepower variants. Mechanical horsepower (745.699872 W), metric horsepower (735.499 W), and electrical horsepower (746 W exactly) are all slightly different values with the same name. This tool uses mechanical horsepower, the standard for automotive and most engineering contexts, but always check which definition a manufacturer's spec sheet is using if precision matters.

Finally, remember that power (watts, horsepower) and energy (watt-hours, joules) are related but different concepts, power is the rate at which energy is used or produced, while energy is the total amount over time. This tool only converts power units, not energy units.

Real-World Use Cases

Automotive: comparing an engine's horsepower rating against a competitor's kilowatt rating when cross-shopping vehicles sold in different markets.

HVAC and appliances: converting an air conditioner or heater's BTU/hour rating to watts when sizing a home electrical circuit or comparing units listed in different unit systems.

Electrical and mechanical engineering: converting motor, generator, or pump power ratings between kW, hp, and MW when specifying or comparing industrial equipment, or sizing a generator against the combined horsepower of the equipment it needs to run.

DIY and home improvement: checking whether a generator's kW rating can handle an appliance's horsepower-rated motor, such as a well pump or air compressor.

Frequently Asked Questions

How many watts are in 1 horsepower?

1 mechanical horsepower equals approximately 745.7 watts, or 0.7457 kilowatts. This is the standard conversion used for motor and engine ratings.

How do I convert an air conditioner's BTU rating to watts?

Divide the BTU/hour rating by roughly 3.412 to get watts, or use this tool by entering the BTU/hour value and selecting Watts as the target unit.

How many kilowatts is a typical car engine?

A 150 horsepower car engine, a common rating for compact and mid-size cars, converts to about 111.85 kilowatts. European and many Asian markets list engine output in kW rather than horsepower, so this conversion is useful when comparing a US-spec horsepower figure against a metric-spec kilowatt figure.

What does "ton" mean on an air conditioner, and how does it relate to watts?

In HVAC, a "ton" of cooling capacity equals 12,000 BTU per hour, a unit that originated from the cooling power of melting one short ton of ice over 24 hours. Converted, 12,000 BTU/hour equals about 3,516.85 watts (roughly 3.52 kilowatts) of cooling power, not electrical input power, which is why an AC unit's power draw on your electric bill is a separate, usually much smaller, number.

Why do the US and most other countries rate engines differently, horsepower vs kilowatts?

Horsepower is a customary unit that originated in the 18th century as a marketing comparison between steam engines and actual horses, and the US, UK, and a few other countries kept using it for vehicles and machinery. Most of the rest of the world adopted the SI kilowatt for official engine ratings once metrication took hold. Both measure the same physical quantity, power, just in different units, so a car can legally be advertised in kW in Germany and hp in the US for the exact same engine.

Is electrical power (watts) the same kind of power as mechanical horsepower?

Yes, power is power regardless of whether it's electrical, mechanical, or thermal, watts and horsepower both measure energy transferred per unit time, and the conversion factor between them (1 hp = 745.699872 W) is fixed and exact for mechanical horsepower. This is why an electric motor's power rating in watts can be directly compared to a gasoline engine's rating in horsepower using this converter.