Free Power Converter Online

A power converter restates a rate of energy transfer from one unit into another — watts from an appliance label, horsepower from an engine spec, BTU per hour from an HVAC datasheet — without you needing to remember which conversion factor applies to which country's convention. This one covers six units: watts (W), kilowatts (kW), megawatts (MW), mechanical horsepower (hp), metric horsepower (metric-hp), and BTU per hour (BTU-h), and it draws a distinction most quick converters blur past entirely: mechanical horsepower and metric horsepower are not the same unit, despite sharing a name.

How the Power Converter Works

Type a wattage into the single input field and the output pane populates automatically, usually within about a third of a second of you pausing, restating that same power figure in kilowatts, mechanical horsepower, BTU per hour, and metric horsepower all at once. That live recalculation is on by default; a toggle in the tool's header swaps it for a manual Convert button instead, in case you want to finish entering a multi-digit number before anything updates. Once a result appears, a Copy button places the full breakdown on your clipboard, a Save button exports it as a text file, and a Clear button empties both fields for the next figure. No account or download is needed to use any of it. The same watt-to-everything conversion is also exposed as a metered API endpoint for anyone building an app or script around it — the request format is documented at /docs.

As a worked example: typing 5000 into the field — 5,000 watts — returns 5 kW, 0.005 MW, roughly 6.7051 mechanical horsepower, approximately 6.7981 metric horsepower, and about 17,060.7 BTU per hour, all recalculated from the same instant the figure is entered. Every one of those five figures traces back to the same six watt-based factors used throughout this page, never a rounded approximation.

Why People Convert Power Units

Power ratings get quoted in whichever unit a given industry or country happens to default to, and that's exactly where a comparison stalls without a conversion:

• Comparing engine specs across markets. A US engine's horsepower rating needs reconciling against a European spec sheet that lists the same engine in metric horsepower — PS, CV, or PK depending on the country — instead of kilowatts. A 150 kW engine, for example, is rated at roughly 201.15 mechanical horsepower or about 203.94 metric horsepower — two numbers that look close enough to pass for each other but aren't quite identical.
• Sizing electrical circuits or generators. Appliance labels list watts, but breaker capacity and generator output are usually rated in kW, so a load calculation needs every device in the same unit before the numbers can be added up. A household running six 1,500-watt appliances at once, for instance, is drawing 9 kW total, a figure a generator's kW rating needs to cover with headroom to spare rather than matched exactly, since most generators are rated for continuous output well below their peak surge capacity.
• Comparing HVAC capacity ratings. Heating and cooling capacity is often listed in BTU per hour on one datasheet and in kW on another, particularly when comparing a furnace against a heat pump. A heat pump rated at 3.5 kW of heating capacity, for example, corresponds to roughly 11,942 BTU per hour on a furnace-style spec sheet.
• Shopping for motors and pumps. Older or imported equipment nameplates sometimes use metric horsepower, while a US buyer is used to reading mechanical horsepower, and the two numbers don't match without converting. A pump plate stamped "10 PS," for instance, is delivering about 7.355 kW, roughly 9.863 mechanical horsepower rather than a clean 10 — close enough that a buyer skimming the nameplate could easily assume it means exactly 10 hp and spec the wrong pump for the job.
• Planning solar or renewable-energy setups. A panel array's rated output in kW or MW needs comparing against an individual appliance's wattage draw before you can size a system correctly. A 6 kW residential solar array, for example, needs to be checked against a household's combined wattage draw across every appliance running at once, not just its single largest device.

Understanding How Each Power Unit Is Defined

Unit	Symbol	Exact value in watts
Watt	W	1 — the SI base unit: one joule per second
Kilowatt	kW	1,000 W
Megawatt	MW	1,000,000 W
Mechanical horsepower	hp	745.699872 W — derived from James Watt's original standard of 550 foot-pounds of work per second
Metric horsepower	metric-hp	735.49875 W — defined as 75 kilogram-force-meters per second, also written PS, CV, or PK depending on the country
BTU per hour	BTU-h	0.293071 W — one British thermal unit of heat delivered per hour

The two horsepower units are close enough to get casually swapped, but they aren't interchangeable, and the gap is large enough to matter on a spec sheet. Mechanical (also called imperial) horsepower is defined from James Watt's late-18th-century standard: a rate of work equal to 550 foot-pounds per second, which converts to 745.699872 W. Metric horsepower — variously labeled PS (Pferdestärke) in Germany, CV (cheval-vapeur) in France, or PK in the Netherlands — is defined instead as 75 kilogram-force-meters per second, which works out to 735.49875 W. The result is that 1 mechanical horsepower equals roughly 1.0139 metric horsepower, a difference of about 1.4%. That sounds small, but on a 300-horsepower engine, mixing up the two units means a discrepancy of about 4 horsepower — enough to matter when comparing two manufacturers' published figures for what should be an identical spec, which is exactly why this converter keeps hp and metric-hp as two separate, independently defined units instead of treating them as interchangeable.

Approach	Tradeoff
Standardizing on watts or kW	Matches SI and every electrical-engineering formula directly, but doesn't match how engines and motors are traditionally marketed
Using mechanical horsepower	Matches US, UK, and most English-language automotive and engine marketing, but is a different number from the metric horsepower used on the same category of equipment sold in continental Europe or Japan
Using metric horsepower	Matches European and Japanese engine and motor nameplates, but easy to mistake for mechanical horsepower since both abbreviations aren't always printed side by side
Using BTU per hour	Matches how HVAC equipment is marketed in the US, but requires converting before comparing against any kW-rated appliance

Whichever unit ends up on the page or the nameplate, the tool always works from the same six exact factors above, so no display choice ever trades away precision — the mechanical-versus-metric horsepower distinction in particular stays intact rather than getting quietly averaged away.

Power Converter vs. Manual Methods and Other Tools

• Running the numbers by hand. The mechanical-to-metric horsepower factors alone (745.699872 versus 735.49875) are easy to mix up or transpose a digit on, since both numbers look similar at a glance, and a single transposed digit produces an answer that still looks plausible instead of obviously wrong.
• A rule-of-thumb multiplier from a forum post. Close enough for casual conversation, but it rounds away exactly the kind of small discrepancy that matters when comparing two manufacturers' claimed output, which is the whole point of running the conversion in the first place.
• An engine spec sheet's own conversion footnote. Useful if you're staying inside that one document, but not something you can reuse for a different engine, appliance, or unit pair without digging up another footnote each time.
• This tool. Exact factors for both horsepower definitions, updated together with watts, kW, MW, and BTU/h from a single typed number, plus the same math available through the API for anyone converting a batch of ratings rather than checking one at a time.

How Your Input Is Handled

The conversion happens entirely inside your browser tab the moment you stop typing — your wattage figure is never sent to a server to generate the multi-unit result, so there is nothing in transit for anyone to see. No account or sign-in is involved, and nothing you enter is stored once you clear the input or navigate elsewhere.

Common Questions About Converting Power Units

Is 1 horsepower always exactly 745.7 watts?

Only for mechanical (imperial) horsepower — 745.699872 W, to be precise. If a spec sheet is using metric horsepower instead, which is common outside the US, UK, and a handful of other countries, the correct factor is 735.49875 W, not 745.7. Mixing the two up is one of the more common horsepower-conversion mistakes.

Why do European car ads list "PS" instead of horsepower?

PS stands for Pferdestärke, German for "horsepower," and it's the metric horsepower unit — 735.49875 W rather than the 745.699872 W used by mechanical horsepower. France uses the near-identical CV (cheval-vapeur) and some other countries use PK; all three refer to the same metric-horsepower definition, just abbreviated differently by language.

How many watts does a typical air conditioner's BTU/h rating represent?

One BTU per hour equals 0.293071 W, so a 12,000 BTU/h air conditioner — a common residential "1-ton" unit — is delivering roughly 3,517 W of cooling capacity. That figure describes heat-transfer capacity, not the electrical wattage the unit draws to run, which is typically a fraction of the BTU/h figure depending on the unit's efficiency.

What's the difference between power and energy, and does this tool convert both?

Power is a rate — how fast energy is being transferred, measured in watts, horsepower, or BTU per hour — while energy is a fixed quantity, measured in joules or kilowatt-hours. This converter handles only the rate side, power; the Energy Converter handles the total-quantity side, and multiplying a power figure by a duration of time is what connects the two.

Why doesn't a car's horsepower rating directly tell me its top speed?

Horsepower measures the rate at which an engine can do work, but top speed also depends on the vehicle's weight, aerodynamics, gearing, and how that power is delivered across the engine's rev range — none of which a single horsepower figure captures on its own.

Do kilowatts and megawatts ever get confused with each other in real specs?

Occasionally, and the stakes are higher than with most unit mix-ups — a small generator rated at 5 kW producing only 5,000 W is a very different machine from a power plant turbine rated at 5 MW, or 5,000,000 W, a thousandfold difference. The megawatt unit exists specifically because utility-scale generation, transmission, and large industrial motors routinely operate at a scale where kilowatts alone would mean writing out an unwieldy number of digits.

Related Tools

Power and energy are directly related — power is energy divided by time — so figures that started life as a one-time energy amount belong with the Energy Converter instead. Motor and engine specs often pair a power rating with a shaft speed, which the Frequency Converter covers for rpm-based figures, and mechanical power problems involving force and speed pair naturally with the Speed Converter. Anyone comparing an engine's output against how far it moves a vehicle per unit of fuel will also want the Fuel Economy Converter.