Power Converter

Electrical, mechanical and thermal power

This converter supports watts, kilowatts and megawatts for electrical power, metric and mechanical horsepower for engines and motors, plus BTU per hour, foot-pounds per second and calories per second for heating and physics.

It distinguishes metric horsepower (735.5 W) from mechanical horsepower (745.7 W), a difference that matters for accurate engine specs.

Common power conversions

• Horsepower to kilowatts and kW to hp
• Watts to horsepower for motors
• BTU/hour to watts for HVAC sizing

Key features at a glance

• Electrical: watts, kilowatts, megawatts
• Mechanical: metric and mechanical horsepower
• Thermal: BTU per hour, foot-pounds per second, calories per second
• Live conversion table updates as you type
• Distinguishes the two horsepower definitions
• Runs entirely in your browser, even offline

Power versus energy

Power and energy are often confused, but the difference is fundamental: energy is a quantity, while power is the rate at which energy is used or produced. The SI unit of power, the watt, is one joule per second. A 100-watt bulb uses 100 joules every second it is on, so power tells you how fast energy flows, not how much in total.

This distinction explains the units. A kilowatt is a rate of power; a kilowatt-hour, despite sounding similar, is an amount of energy (a kilowatt sustained for an hour). Keeping the two straight matters when reading appliance ratings or engine specs: the wattage or horsepower describes capability, while the energy bill depends on how long that power is drawn. This converter handles power units; energy units have their own converter.

The two definitions of horsepower

Horsepower is not a single unit, which surprises many people. Mechanical (imperial) horsepower, the figure common in the US and UK, equals about 745.7 watts, while metric horsepower — often written PS or CV in European specs — equals about 735.5 watts. The roughly 1.4% difference means the same engine can be quoted with slightly different horsepower numbers depending on the standard used.

The term itself dates to James Watt, who coined it to market his steam engines by comparing them to the draft horses they replaced. He estimated the sustained power of a horse and rounded it into a memorable unit. The converter keeps the metric and mechanical definitions separate so that when you compare engine or motor specifications from different regions, you are comparing like with like rather than being misled by the definition.

Power across electrical, mechanical, and thermal domains

Because power is one quantity, electrical, mechanical, and thermal units all interconvert. Electric motors are rated in kilowatts or horsepower, heating and cooling equipment in BTU per hour, and physics problems often use watts directly. An air conditioner's '12,000 BTU/hour' cooling capacity, for example, corresponds to about 3,517 watts of heat moved.

This cross-domain reach makes the converter useful for sizing and comparison tasks. Matching a generator's kilowatt output to the horsepower of the engine driving it, or comparing an electric motor with the internal-combustion engine it replaces, requires moving between units that different industries prefer. Having them all in one place, with the horsepower definitions clearly separated, removes a frequent source of specification errors.

Tips for converting power

• One mechanical horsepower is about 745.7 watts; metric horsepower is 735.5 W
• Watch for PS or CV in European specs — that is metric horsepower
• Power (watts) is a rate; energy (kilowatt-hours) is a total amount
• HVAC capacity in BTU/hour converts to watts for comparison
• One kilowatt is about 1.34 mechanical horsepower

Why choose our power converter?

Our converter is completely free with no signup, no limits, and no subscription. It runs entirely in your browser, so conversions are instant, it works offline, and the values you enter never leave your device.

It is one of more than 200 free tools on ToopTools, and you can pin it to your My Workspace, a personalized workspace where you keep the tools you use most in a single dashboard. Beside the other unit converters, it covers electrical, mechanical, and thermal power in one place.

Common use cases

People use the power converter to compare engine and motor specs across regions, where horsepower definitions differ, and to translate appliance and HVAC ratings between watts and BTU per hour. It makes specifications from different industries directly comparable.

Engineers size motors and generators by converting between kilowatts and horsepower, HVAC professionals work in BTU per hour, and students solve physics problems in watts. Because every unit appears at once and the two horsepower definitions are kept separate, the converter avoids the subtle errors these conversions often introduce.

Is the power converter free?

Yes. It is completely free with no account, no sign-up, and no usage limits. Convert as much power as you like at no cost.

How many watts are in one horsepower?

Mechanical horsepower is about 745.7 watts, while metric horsepower (PS) is about 735.5 watts. The converter keeps the two separate so you compare engine specs accurately.

What is the difference between power and energy?

Power is the rate of energy use, measured in watts (joules per second), while energy is the total amount, measured in joules or kilowatt-hours. A device's wattage is its power; how long it runs determines the energy used.

Why are there two kinds of horsepower?

Mechanical horsepower (about 745.7 W) is used in the US and UK, while metric horsepower (about 735.5 W, written PS or CV) is used in Europe. They differ by about 1.4%, so the same engine can be quoted slightly differently.

How do I convert BTU per hour to watts?

Multiply BTU per hour by about 0.293 to get watts. For example, a 12,000 BTU/hour air conditioner moves about 3,517 watts of heat, which is useful for comparing cooling capacity.

Are my conversions kept private?

Yes. Everything is computed in your browser and nothing is uploaded, so the values you enter stay private and the tool works without an internet connection.

How do I convert horsepower to kilowatts?

Enter a value in horsepower and pick kilowatts as the target, and the converter shows the result instantly. It also covers watts, megawatts, and BTU per hour, so you can switch between engine, electrical, and heating power units in a single step.

Does the power converter work offline?

Yes. The conversion runs entirely in your browser, so once the page has loaded the tool works without an internet connection, and nothing you enter is uploaded — it stays private on your own device.