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Power Converter

Convert watts, kW, MW, hp, BTU/h, ft·lbf/s and more

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Type the amount you want to convert into the power value field.
  2. 2.Choose the unit you are converting from and the unit you want the answer in (for example kW to hp, or watts to hp).
  3. 3.Read the converted result instantly, or tick 'Show all units at once' to see watts, kW, MW, hp, BTU/h and more together.

About Power Converter

A power converter turns any amount of power between watts (W), kilowatts (kW), megawatts (MW), milliwatts (mW), mechanical horsepower (hp), metric horsepower (PS), BTU per hour (BTU/h), foot pounds-force per second (ft·lbf/s), calories per second (cal/s) and kilocalories per hour (kcal/h) — instantly and entirely in your browser, with nothing uploaded. Every unit is converted through one common base, the watt (W), the SI unit of power, defined as one joule per second. Your value is first turned into watts, then divided into the target unit, so every pairing stays consistent.

The conversions people search for most are watts to hp, kW to hp, and hp to watts. To convert kW to hp, divide the kilowatts by 0.7457, because 1 mechanical horsepower = 745.6998715822702 W, so 1 kW ≈ 1.341 hp. Going the other way, 1 hp ≈ 745.7 W = 0.7457 kW. These are the numbers used to rate car engines, pumps and motors, and they are exact by definition rather than approximate.

The single biggest trap in power conversion is that there are two different horsepowers. Mechanical (or imperial) horsepower, used in the United States and the UK, is defined as 550 foot pounds-force per second, which equals exactly 745.6998715822702 W. Metric horsepower — written PS (Pferdestärke), CV or cv, and common on European and Asian spec sheets — is defined as 75 kilogram-force metres per second, which equals exactly 735.49875 W. The two differ by about 1.4%, so a 100 PS engine is roughly 98.6 mechanical hp. This converter lists both separately and never silently mixes them, so you always know which horsepower you are reading. When a source just says 'hp', US material almost always means mechanical hp, while a European PS figure is metric horsepower.

Heating, ventilation and air conditioning is where BTU per hour matters. Air conditioner and heat pump capacity is almost always quoted in BTU/h in North America: a common window unit is 5,000 to 12,000 BTU/h, and 12,000 BTU/h is defined as one 'ton' of cooling. Because 1 BTU/h ≈ 0.293 W, a 12,000 BTU/h air conditioner draws (in cooling capacity terms) about 3,517 W ≈ 3.5 kW, which is why comparing an AC rated in BTU/h against one rated in kW needs a converter. This tool handles that pairing directly, along with ft·lbf/s for mechanical work and cal/s and kcal/h for thermal and metabolic power.

Because these units span a wide range — from the milliwatt to the megawatt, about nine orders of magnitude — the results switch to scientific (exponential) notation at the extremes so no significant figures are lost. Enter any number, choose your source and target units, and read the answer immediately; tick 'Show all units at once' to see watts through kcal/h side by side. Everything runs client-side, so your values never leave your device.

Frequently asked questions

How many watts are in one horsepower?
It depends on which horsepower you mean. Mechanical (imperial) horsepower is exactly 745.6998715822702 W, so about 745.7 W. Metric horsepower (PS) is exactly 735.49875 W, about 735.5 W. To convert hp to watts, multiply by 745.7 for mechanical hp or 735.5 for metric hp.
What is the difference between mechanical and metric horsepower (PS)?
Mechanical (imperial) horsepower, used in the US and UK, is defined as 550 ft·lbf/s = 745.6998715822702 W. Metric horsepower — written PS, CV or cv and common in Europe and Asia — is defined as 75 kgf·m/s = 735.49875 W. They differ by about 1.4%, so a 100 PS engine is roughly 98.6 mechanical hp. This converter keeps the two as separate units so they are never mixed up.
How do I convert kW to hp?
Divide the kilowatts by 0.7457, because 1 mechanical horsepower = 745.6998715822702 W. So 1 kW ≈ 1.341 hp and, for example, 100 kW ≈ 134.1 hp. For metric horsepower (PS), divide by 0.73549875 instead, giving 1 kW ≈ 1.360 PS.
How do I convert a BTU/h air conditioner rating to watts or kW?
1 BTU per hour ≈ 0.293 W, so multiply BTU/h by 0.293 to get watts. A 12,000 BTU/h air conditioner (one 'ton' of cooling) is therefore about 3,517 W ≈ 3.5 kW. This lets you compare North American AC units rated in BTU/h against units rated in kW.
How does this power converter stay accurate?
Every unit is converted through a single base, the watt (1 W = 1 joule per second), using exact factors from NIST SP 811 and the SI definitions. Your value becomes watts, then the target unit, so all pairings agree. For extreme results (for example milliwatts to megawatts) it uses scientific notation so no significant figures are lost.

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