Unit Tools

Free Online Power Converter, Watts, Kilowatts, Horsepower & BTU/h

Convert watts to kilowatts, horsepower to kW, BTU per hour to watts and more. Metric and mechanical horsepower are listed separately because they differ by about one percent, and car specifications quote whichever suits them without saying which one they used.

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Free Online Power Converter, Watts, Kilowatts, Horsepower & BTU/h

There is more than one horsepower. Mechanical horsepower is about 745.7 W. Metric horsepower, written PS and used on most European car specs, is about 735.5 W, roughly 1.4% smaller. This converter keeps them apart, so an engine figure converts the way it was quoted rather than the way you guessed.

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⚡ Power Converter Base unit: Watt · 6 units

Every factor ships with the page. The sum runs in your browser and nothing is sent anywhere.

⚡ Convert power

Pick the two units, type a number, and the answer is already there.

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Amount

Result

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Recent conversions, kept in this browser only.

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Common Power Conversions

Engine sizes included, so you can skip the typing.

Conversion	This	Equals
hp to kW	1 hp	0.7457 kW
kW to hp	1 kW	1.34102 hp
hp to watts	1 hp	745.7 watts
100 hp in kW	100 hp	74.57 kW
150 hp in kW	150 hp	111.86 kW
200 hp in kW	200 hp	149.14 kW
100 kW in hp	100 kW	134.10 hp
metric hp to hp	1 PS	0.98632 hp
kW to metric hp	1 kW	1.35962 PS
kW to BTU per hour	1 kW	3,412 BTU/h
1 ton of cooling	12,000 BTU/h	3.517 kW
MW to kW	1 MW	1,000 kW

Which Horsepower Is Your Number?

There are two, and they are 1.4% apart.

Unit	Symbol	In watts	Where you will see it
Mechanical horsepower	hp	745.70 W	US and UK, most English-language specs
Metric horsepower	PS	735.50 W	European car makers, Japanese specs
Kilowatt	kW	1,000 W	Official SI unit, EU documents, EVs

The same engine can be sold as 150 PS or 148 hp, and neither figure is a lie. If you are comparing two cars from different markets, convert both to kW first. That is the one unit nobody argues about.

How to Convert Power

Four steps, and not one of them needs a server.

Choose watts, kW or horsepower

Watts up to megawatts, plus both horsepowers and BTU per hour. Each horsepower says which one it is.

Type the power

The power appears in the second box as you type. No convert button, and nothing leaves the device.

Check which hp

European car figures are usually PS, English-language ones usually hp. The table on this page tells you which to pick.

Save the pairs you repeat

Save kW to hp, watts to BTU/h or whichever pair you run daily, and pick recent figures back up from history.

Every Power Unit, and What It Equals

All 6 units in this converter, measured against one watt.

Unit	1 unit equals
Watt (W)	1 watt (the base unit)
Kilowatt (kW)	1,000 watt
Megawatt (MW)	1,000,000 watt
Horsepower (mechanical) (hp)	745.699871582 watt
Horsepower (metric) (PS) *	735.49875 watt
BTU per hour (BTU/h)	0.293071070172 watt

* Units marked with a star are approximate by nature. Hover the star to see why.

What This Converter Does

And what it will not quietly get wrong.

Horsepower appears as you type

Type a figure in kilowatts and the horsepower answer is already there, with BTU/h beside it.

Both horsepowers listed

hp and PS as separate units, 1.4% apart. Most converters keep one and decide for you which spec sheet you were reading.

Says what it cannot do

Amps and kVA need voltage and power factor. This page explains why instead of inventing an answer.

BTU/h for heating and cooling

Air conditioners and boilers are rated in BTU/h, so the unit is here alongside the electrical ones.

Your usual power pairs

Keep kW to hp, or watts to BTU/h, one tap away, and pick any recent figure back up where you left it.

Offline once loaded

Every power factor ships with the page, so there is no account to make, nothing to upload and no server to call.

Frequently Asked Questions

What people actually ask about power units.

Multiply by 0.7457. So a 150 hp engine is 111.9 kW. Going back, multiply kW by 1.34102. The rough head sum is "three quarters", which is close enough to picture the number while you are reading a spec sheet.

PS is metric horsepower and it is about 1.4% smaller than mechanical horsepower. One PS is 735.5 W, one hp is 745.7 W. The same engine can be quoted as 150 PS or 148 hp, and neither figure is wrong. European and Japanese makers usually publish PS, so check which one a number came from before comparing two cars.

Match whatever your source used. If the figure came off an American or British spec sheet it is almost certainly mechanical hp. If it came from a European brochure, or the letters PS or CV appear anywhere, it is metric. Both are in this converter as separate units so you never have to assume.

745.7 for mechanical horsepower. The number goes back to James Watt in the 1780s, who measured how much a working horse could lift in a minute so he could sell steam engines by comparison. It has been a defined figure ever since, which is why it is such an untidy one.

Not on its own, and any tool that says otherwise is guessing. Amps depend on voltage: 1 kW is about 4.35 A at 230 V but 8.33 A at 120 V. For AC you also need the power factor. Give it a voltage and the sum is simple. Without one, there is nothing to calculate.

No. kVA is apparent power and kW is real power, and the gap between them is the power factor. A generator rated 10 kVA at 0.8 power factor delivers 8 kW of useful work. Since power factor changes with the load, kVA cannot be converted without knowing it, which is why it is not in this list.

Heating and cooling, mostly in the United States. Air conditioners and boilers are rated in BTU/h. One kW is 3,412 BTU/h, and a "one ton" air conditioner is 12,000 BTU/h, which is 3.517 kW. The ton refers to how much ice it could once melt in a day, which tells you how old the unit is.

They are defined figures, so yes. Mechanical horsepower is exactly 745.6998715822702 W and metric horsepower is exactly 735.49875 W. Those are definitions rather than measurements. The only rounding is how many decimals you ask for in Settings.

No. The watt, kilowatt, horsepower and BTU-per-hour factors are written into the page, so the sum runs on your own machine. The figures you looked up and the pairs you saved stay in this browser on this device, and Settings clears them for good.